Mayank Agarwal
Author: Mayank Agarwal  |  

Mayank is an email marketing expert & co-founder of SendX. SendX is an intuitive & affordable email marketing software.

Read more posts by this author.

If you are reading this it is highly likely that a portion of your emails are landing in SPAM.

You must be pondering - "why are my emails going to spam?", “What did I do wrong in the last few weeks that caused my emails to land in SPAM?”, “Am I being too aggressive with my email marketing campaigns?” Or “Is it the new Email Marketing Provider which we moved to recently?”, "how to make emails not go to spam?", "why do some emails go to spam?".

Before I get deep into the topic, here is a quick preview of what we will be covering in this guide. Meanwhile, if you're looking at quick answers do check out the summary listed at the bottom of the page.

So, back to the question: "why are my emails going to spam?"

The tragedy is:

You don’t have to be a spammer for your emails to land in SPAM.

It is very likely that you were part of the collateral damage in a war being waged against email SPAM.

With this guide we will teach you exactly how to prevent your email from going to SPAM.


For some reason (probably unintentional) your emails mimicked the behavior of a Spammer and they were sent straight to the email graveyard (read: spam folder).

Email gatekeepers
Your emails will get shot down your if your email behaviour is similar to spammers
The goal of this guide is to teach the rules of this war to You (a non-Spammy innocent civilian) so that you can stay off those dangerous territories.

Before we jump into rules, a quick line on how email delivery infrastructure works.

In order to deal with the email SPAM problem, Internet Service Providers (ISPs) and Email Inbox providers (like Gmail, Yahoo Mail, AOL etc.) rely on SPAM filters, Firewalls and Blacklist directories to keep your inbox free of "Unsolicited” SPAM emails.

I would strongly recommend checking out our definitive guide on email deliverability to learn more about how exactly this works.

There is 3 broad class of reasons because of which your email might land in SPAM.

So, this will answer your questions "how to make emails not go to spam"?

A). Your email looks (design, copy, header) like a SPAM email
B). You Domain has a poor reputation
C). The IPs (read: email servers) over which you are sending emails have a poor reputation.

A lot of factors (70+) contribute to the above and here, with this guide, we deconstruct each one of them. Also, if your email is landing in SPAM it is highly likely that you are violating more than 1 law across the 3 classes.

Few Abbreviations & Definitions which I will be using in the article:

ESP - Email Service Provider. By ESP I specifically mean email marketing software (like SendX) that help you send emails at scale.

Inbox Providers - Companies that provide an Inbox for your emails (Gmail, Yahoo Mail. Outlooks, Hotmail, AOL, Apple Mail etc.).

Spam Filters - Decides whether the email should be present in the inbox, promotions tab, spam folder or whether it should be blocked all together.

IP Address - Internet Protocol Address. In this article's context it refers to the unique public address of the server over which your emails go. This is typically maintained by the ESP.

Laws that rule the Spam world

Now, let's get started with deconstructing all the LAWS of the SPAM WORLD and answer the question which every email marketer encounters at some point in their career - "why are my emails going to spam?"

A). Your Email Looks (design, copy, header) Like a SPAM Email

The spam filters and firewalls take a look at the anatomy of your email, match it with commonly occurring themes (of a SPAM email) and decide if your email is SPAM or not.

Here are all the various factors that a spam filter takes a look at:


1). Keywords in your email body

These are also known as SPAM trigger words. It is highly likely for an email to be SPAM if these keywords are frequently present in your email. With highly sophisticated AI and Machine Language being used inside SPAM filters, this subject is more complicated than just simple words being present and their frequency. Always take an objective look at your email and see if you're being too pushy or salesy.

Here are the words that you should either avoid entirely or at least avoid overusing:

  • lottery
  • cancel at any time
  • check or money order
  • click here
  • congratulations
  • dear friend
  • for only ($)
  • free or toll-free
  • great offer
  • guarantee
  • increase sales
  • order now
  • promise you
  • risk free
  • special promotion
  • this is not spam
  • prize
  • free
  • bonus
  • buy
  • purchase
  • order
  • amazing
  • money back guarantee

2). Keywords in your email subject line

Pretty similar to the above point. Avoid using pushy words in your subject line and stay away from words like (lottery, prize, fortune etc...).

3). Image / Text ratio

A common trick used by spammers is to hide all SPAM trigger words in an image and use the email body for neutral words only. Since most SPAM filters do not process the image it gets past them. So, an email with a really skewed ratio of Image/Text can start getting flagged by SPAM filters.

4). Alt Text not present in images

Some users don't allow display of images in their in inbox. The images in your email won’t show to them, making your email look spammy. This can further lead to them marking the email as SPAM. SPAM filters will take this feedback and over a period of time will start considering most of the emails with a similar signature as SPAM.

A simple way to handle this is to use Alt text with your images. Alt text is a text that shows when ever the image is not displayed.

Example of email with Alt Text
Example of Email with Alt Text

5). Similar email being marked as SPAM by users

This is how SPAM filters learn new email SPAM patterns. If your emails are landing in SPAM and Gmail is giving a message like the following, it is time to change the copy and HTML templates of your email.

Email marked as Spam

The best course of action is:

a). Click the "Report not spam" button

b). Change your email copy

c). Change your email template. You can choose from 1500+ emails templates we have collected for you or download our premium email templates.

Start a Free Trial
No credit card required. Instant setup.

You might also want to use a spam checker to analyse if you’re going through the tunnel to reach every customer, or if your email is going to get spammed.

If the links inside your emails point to a suspicious domain or a URL which has been flagged as fraudulent then it is very likely your email will land in SPAM.

Beware - This can also happen if you are using an email marketing software and the domain they use to re-write links (to track link clicks) is spammy.

You can try SendX if this is happening to you. We ensure that this never happens with our customers.

7). Using URL shortener in email

This might come as a surprise. But, the reason for this is simple - A lot of Spammers use URL shortening services like to hide their spammy URL(as they all have access to the same domain and appear the same). Never use generic link shorteners in your emails. However, if you do need to use them, we recommend you use one that allows you to brand the links that you shorten, such as Rebrandly URL Shortener for example. This way you remain in control of your links as you are able to put your brand on your link, which leads to increased trust while avoiding spam filters.

You can find the most abused URL shorteners over here


Email world is required to adhere to SPAM Laws like CAN-SPAM Act (by US Govt.), Canada’s Anti-Spam Legislation (CASL) and GDPR (by EU).

These laws lay down guidelines and not following them will not only attract heavy penalty (according to the FTC, if you violate the law, you could be fined $11,000 for each offence—that’s $11,000 for each email address on your list). Here are a few things to keep in mind:

All marketing emails need to have a clear way for users to opt-out of them. If you are sending emails to opted-in list(s) ensure every email going to them has a way to opt out of using an unsubscribe link.

All opt-in emails need to have the physical address of the company (in the email footer).

Address in the Email Footer
Address in the Email Footer

This is not mandated by law (considering you have an unsubscribe link in the email footer) but email providers like Gmail consider this an important signal of reputation. This is how the unsubscribe link in the header looks like:

Unsubscribe link in the Email Header
Unsubscribe Link in the Email Header

Use SendX to ensure all your emails follow the above Guidelines

11). Missing 'From Name'

This can happen if you forget to add this while creating your email campaign and the email marketing software you use does not stop you from sending the campaign. Most of your emails will land in SPAM folder and also your domain and IP reputation will take a hit.

12). Missing 'Subject Line'

This can again happen in case you missed adding a subject line while creating your email campaign and the email marketing software does not stop you from sending the campaign. Again, almost all your emails will land in SPAM folder and giving a beating to your domain and IP reputation.

13). Missing 'Email Body'

Same as above. If you missed adding the email body itself while creating your email campaign and the email marketing software does not stop you from sending the campaign.

Missing email body
Missing Email Body

14). Missing Plain Text version of your email

This is applicable in case you are sending HTML emails.

Every HTML email should have a plain text version.

There are three reasons for this:

a). Spam filters prefer a plain text version.

b). Some email users prefer text emails.

c). Email provider serves this email version for users on a slow internet network.

Unless you are sending a simple plain-text email, multi-part MIME should be part of every email.

Multi-part MIME (Multipurpose Internet Mail Extensions) bundle together a plain text version of your email along with the HTML version.

As Tom Burke explains:

A multipart MIME message is like a package with multiple boxes within it. In your standard HTML + text message, both types of content are sent in the email. Your email client, assuming it understands MIME format, will decide which of the boxes to open and display to you."

We at SendX, automatically generate a plain text version when ever HTML email, so if you are using SendX for your email marketing, you can consider this steps as done.

15). Different versions of HTML and plain text email

This adds on to the above point. Ensure you are not having two different messages in your HTML & plain text versions. You don't need to be too clinical about it, just ensure that your email does not signal anything suspicious to spam filters.

Again, SendX takes care of this for you as well by auto-generating the plain text version of the HTML email.

Start a Free Trial
No credit card required. Instant setup.

16). Broken HTML

Broken HTML will appear sloppy and unreadable on certain (or all) email clients. Not only will users mark your email as SPAM, but it will also alert SPAM filters (they will think you could be a lazy spammer using unsophisticated tools).

An important note here - I have seen way too often, marketers copy content directly from Microsoft Word, Excel, Powerpoint, etc. Beware, these applications add additional unwanted characters to your message source. Always copy your content to a plain text editor that strips off all such characters.

All templates we offer for free and every template inside SendX is tested to ensure HTML is done.

Email with broken HTML
Email with broken HTML

17). Email Size > 100KB

Now, the debate is out if email size impacts your SPAM score. Email Acid team did a test on this and this is what they had to say:

We created text-only, HTML emails in various sizes, from 15-650KB.
We found that sending a file size between 15KB-100KB is A-OK. These emails successfully passed through all our spam filters with flying colors!
Deliverability issues began to occur once the email file size was over 100KB. Every email from 110KB to 650KB wound up failing multiple spam filters. Interestingly enough, once the email file size was over 100KB, the number of spam filters that failed each email stayed the same. For example, an email that was 110KB got caught in the same 7 spam filters as an email with a file size of 650KB.

Multiple studies point that there is a correlation between email size and deliverability. We would recommend keeping emails between 15KB-100KB to ensure healthy deliverability.

18). Unsafe OR binary attachment

This is an obvious one. Scammers use this technique to steal your data. You would see a warning in Gmail like this:

Unsafe email warning
Unsafe Email Warning

19). Image only email

Here are the reasons we think sending image only emails could be bad for you:

a). Typically email clients don't parse the text and hence this technique has been used by spammer. Your emails will get shot down by spam filters and firewalls that place a high weight on this.

b). Image only emails will likely have an empty text field (refer point #14).

c). Some email users don't allow display of images by default. For them, your email will come as empty (with only Alt text if you have followed point #4). Your email will look spammy to them. They can even mark your email as spam.

It is better to be safe than sorry in such grey areas. Avoid sending emails with a single image in them.

20). Non-responsive email design

This in itself will not directly cause your emails to land in SPAM.

But, considering that the majority of emails are now opened on a mobile device the likely hood of users marking your email as SPAM will increase if the email does not render properly (who can blame them?).

We understand the importance of responsive template in email marketing. All email templates inside SendX are responsive by default. Not only that, we have created one of the biggest responsive email templates resources on the web (till date). We have crafted some of the most beautiful email templates and offer them for free for our fellow #email #geeks :)

Example of non-responsive email design
Example of Non-responsive Email Design

21). Using unsupported HTML tags and CSS attributes

Like the point above, this in itself will not directly cause your emails to land in SPAM. But, an Email that does not render properly will start getting marked as SPAM.

Here is the thing: Email HTML is NOT equal to Web HTML.

There are a lot obvious HTML tags and CSS attributes that are not supported by major email clients (major culprit being - Microsoft Outlook). The safest way to design an email is to use HTML tables. PERIOD.

22). Using JavaScript in your email HTML

The problem with doing anything smart with email (i.e using scripting languages like JavaScript) is then that email is no longer safe.

Spam filters and more importantly firewalls always take a "better to be safe than sorry" approach. So, all your well-intentioned emails with any type of script will go straight to the SPAM folder.

23). Using iframe tag

An iframe is an HTML element that embeds content from one website into another. Iframes more often than not contain scripts and will simply get blocked.

Instead of using iframe use a link to your content you want to embed.

24). Using flash

Most email clients simply don't support flash content as it is considered unsafe for something as sensitive as email. Email clients block emails containing flash.

You can use GIFs as an alternative to make your emails more appealing.

25). Using HTML forms

Avoid embedding forms in your email. The submit button of the form will require you to use JavaScript (which is a problem).

26). Using rich media content

All major email clients don’t allow the ability to view rich media content as they don't support HTML5.

Remember: Email HTML is NOT equal to Web HTML.

The email with this type of content will look spammy to most of your users and will ultimately lead to emails getting marked as SPAM (if they make it to the inbox).

27). Spelling and Grammar Errors

Poorly Written Email Copy

Sounds obvious? Not really. If you are a psychology junkie, the reason for this might blow your mind.

This is the secret reason why most scam emails are poorly written - It is not because the scammer has poor English or he is lazy. It is because a poorly written email self selects the most gullible victim. Read the last sentence again. Now. Done?

What would you do if you really get scammed - Report it to the police.

This is a bad outcome for a scammer. They would rather want you to ignore the email Or mark it as SPAM, which is what a poorly worded email does!

It self selects people who are at the bottom of the pyramid because of

a). They would fall for it easily (blind spot due to lack of knowledge + greed)

b). They might not have the resources to come after you (once they are scammed).

And...I didn't come up with this theory. Check out this paper from Microsoft Research that talks in depth about this topic.

You will find very similar patterns in phishing emails as well.

Mind = Blown


This is how I reacted as well!

Okay, enough of a detour. So, why did I tell you this?

a). Any of these obvious and stand out slips in spelling abd grammar will alert SPAM filters.

b). Obvious, but, worth repeating - the user will mark the email as SPAM hence indirectly affecting your reputation.

So, here are things you should avoid:

28). Big Fonts and Flashy Color

29). A lot of Exclamations!!!!! and $$$$$$


30). Using phishing phrases

This will typically happen only if you are sending emails in an unauthenticated manner or using brand names in the emails which are most regular victims of Phishing attacks.

31). Malformed From Email address  

Avoid frequent changes to the From email address field and avoid obscure From email fields like, We strongly recommend our users to use trustworthy email addresses like “feedback@”, “newsletter@”, “support@”, "hello@”, <your_name@> etc.

We can't tell for sure if this goes as a direct signal to SPAM filters but we have seen emails with trustworthy addresses getting much better open rates. Also, weird obscure email addresses can make some users mark them as SPAM (affecting your domain and IP reputation).

B). Domain Reputation:

Your domain (which you use to send emails) reputation plays a vital role in your email deliverability. To borrow an analogy from the finance world, it is a lot like a credit score for your email domain. If it is high, you will get good deliverability. We have seen it is equally hard to reverse a bad domain reputation and impersonation techniques (like using a new domain/sub-domain to send emails) rarely work. With SPAM filters getting really sophisticated it is getting impossible to be a bad citizen in the world of email without permanently damaging your domain reputation.

Spamming journalists with PR releases with emails can hurt your reputation and make all your other non PR emails go to spam as well for recipients, or worse get your email account banned.

That said, let's deconstruct what are the factors that contribute to it.

32). Purchased email list

If your email list is purchased then a portion of your email receipts will mark your emails as SPAM and you will have a high bounce rate.

33). People marking emails as SPAM

This should not come as a surprise. If people mark your emails as SPAM, your domain reputation will get effected.

When your subscribers click on Mark as SPAM,  a SPAM complaint is logged by mailbox providers like Gmail, Yahoo, AOL, Outlook etc. notifying ESP's about the same.

Since SPAM complaints are an explicit user signal about unsolicited emails (even a 0.5% SPAM rate is considered really high).

SendX automatically removes all email addresses from your list as soon as we detect they have marked your email as SPAM for the first time. This ensures that you do not send any further emails to those users. We do this to protect the domain reputation of legitimate users.

Start a Free Trial
No credit card required. Instant setup.

34). Email Bounces

There are 2 type of Email Bounces:

a). Hard Bounce - Hard Bounce is an email message which bounces back OR returns to the sender because the recipient's email address is simply wrong (invalid).

b). Soft Bounce - Soft Bounce are temporary failures because recipient's email mailbox is full, down or out of office.

Hard bounce vs Soft bounce
Hard Bounce Vs Soft Bounce

Hard bounces affect your domain reputation much more than soft bounces since it is a clear sign that something is wrong with your email list.

You should get alerted if your email campaign has > 5% bounce rate.

SendX automatically removes all hard bounce email address from your list as soon as we detect it for the first time. This ensures that your domain reputation does not get spoiled by repeated email bounces.

35). Gmail users blocking your emails

This feature was introduced by Gmail in 2015. If someone blocks your email, you will never be allowed in there inbox again (until they unblock you). Needless to say if this happens a lot with the emails from your domain then your domain reputation will take a toll.

36). An unusually high number of abandoned emails in your list

For SPAM filters this smells more like a purchased list. List sellers bloat up their list size (to sell at a higher price) with abandoned emails.

37). Having SPAM trap emails in your list

These are like the secret agents of SPAM filters.

Secret agent of Spam filters

They are fake email addresses which are published in a hidden location of the web. The only way these email addresses can be a part of an email list is when some has crawled the web and collected email addresses.

38). Using free email address as your From Email address

If you are using an ESP (like SendX) then you will need your own domain to send emails. The reason you can not use free email address inside a 3rd party system is that they have strict DMARC policies.

If you have your own domain you can set DMARC policies that will tell receiving servers how to handle emails that have failed the DMARC check.

Using a free email address

39). Not having a valid website

This is a typical behavior of a spammer. They keep buying new domains to send emails (and do not really create a website on that domain which you can easily do with an unlimited hosting plan). In case you are buying domains to only send emails, ensure you either redirect that domain to parent business website or host a simple page like this. This is important for insurance agents who buy a domain to send email but never design an insurance website. If you're shopping around for the right hosting provider, check out some of the best hosting plans in the market today.

40). Inconsistent Email Volume

This again is typical behavior of a Spammer. Also, can you think for legitimate business who will suddenly increase their email volume by 100x?

Sudden changes in email volume is always considered suspicious in the email world.

Email Authentication

Email authentication is an important topic if you are using a 3rd party ESP (like SendX). If you are using a mailbox provider like - Gmail, Yahoo Mail, AOL, Apple Mail etc then your emails will be authenticated by default (if everything is setup correctly).

Quite simply, email authentication means - that you (owner of the domain) are giving required permissions to a 3rd party ESP, to send emails on your domain's behalf.

In case you are wondering if it is even possible to send emails from a domain without providing permission (from the domain owner), the answer is YES. You would have seen emails having via <some_domain_name> in the email header like following.

Email authentication via another domain

If not, go check your inbox and you are sure to find several emails like this. This simply means Johnny Appleseed's domain is sending this email over the authentication of domain. To read in-depth about email authentication I would recommend reading the Email Authentication section of our Email Deliverability guide.

Needless to say, this is not the best way to send emails. And SPAM filters look at such an email with suspicion. A lot of spammers also rely on this technique since they are able to leverage the good domain reputation of the ESP.

Always ask for your ESP to provide email authentication. At SendX, we provide email authentication for free in every plan and strongly encourage our users (during on-boarding) to get their domain authenticated with SendX.

Here are common mistakes we see people make (when it comes to email authentication):

41). Not adding SPF Records

It stands for Sender Policy Framework. It is an email authentication method to detect forged sender addresses in emails. It is a TXT DNS record entry which allows an IP or a set of IPs or email servers to send emails for you. All emails not originating from these servers will be considered as unauthenticated. Email inbox providers check this to either reject the mail entirely or send them to Spam of the receiver's email ID (so that no one else exploits you as a sender). It is a best practice not to allow more than 10 servers to send emails on your behalf.

To test this, you can open any email that you received and check the headers and/or the original mail. The "mailed by" domain tells you whether or not the SPF is applied properly. It should match the domain of the from email address.

Check Headers and original email

In inbox providers like GSuite, there is a simplified description of the header in the original email stating whether the SPF passed.

SPF records Header in Gmail
SPF Records Header in Gmail

You can also lookup for your SPF Records here.

42). Not adding DKIM Records

It is the abbreviation for Domain Keys Identified Mail. It provides a mechanism to verify that the email message has come from the domain it is claiming to and the message hasn't been tampered with along the way. This is done using a two-way (private key and public key combination) authentication. The public key is usually supplied by the ESPs (again, in the form of a TXT DNS entry which can be queried globally) and the private key is used by themselves to encrypt the entire or a part of the email, which can be decrypted on the receiving end by using the public key. If the decryption fails, the receiver knows that either the domain hasn't allowed this email to be sent or somebody in between has tampered the email (man-in-the-middle attack).

To check whether your DKIM is valid, you can check the email headers and look for "signed by".

Check email Headers for Signed by

In inbox providers like GSuite, there is a simplified description of the header in the original email stating whether the DKIM passed

DKIM records in email Header
DKIM Records in Email Header

You can also lookup for DKIM here.

43). Not adding (or incorrectly adding) DMARC

DMARC is a declaration from the sending domain that their owner knows about email authentication and receivers should receive fully authenticated emails (including both SPF and DKIM) originating from them. It also declares what actions should be done to emails not having the proper authentication. They may include: letting them be or not affecting them, sending them to the spam folder or blocking such emails entirely. When DMARC is added for any domain, it can be configured so that inbox providers like Gmail, Outlook, Yahoo etc can send regular email reports as to how many emails were encountered with/without proper email authentication and what actions have been taken.

This can be added directly by domain owners following the steps in Although the absence of DMARC doesn't cause emails to land in Spam folders currently, most email inbox providers are fighting towards mandating this since the domain owners are much more in charge and help fight email spam globally.

DMARC entry can be checked in the original email data and inboxes like Gmail also provide simplified headers for it.

44). Using via Domain

If ESP doesn't provide you with authentication/whitelisting details(SPF/DKIM), then they are using their own domains to send your emails. These temporary domains are authenticated by the ESPs themselves. This means that not only would your emails go over their servers, but also, your email deliverability would depend on the reputation of these via domains which might be used for their multiple clients with variable email sending habits. This could impact the deliverability and open rates of your campaigns heavily.

You can check the "mailed by" and "via" domains to validate your settings.

Check Mailed by and Via Domains

45). Domain Present in Email Blacklists

Domain blacklists are quite simply a directory of domains that have been involved in suspicious behavior.  

A lot of publicly available blacklists (300+) have been created. SPAM filters refer to one or more of these blacklists.

Check if your domain is in any blacklists.

We proactively help our users with getting them delisted from these blacklists. Do reach out to us for more help in this regard.

46). Domain Age

This one might sound obvious, but in the email world this is even more important.

It is much easier to spoil your reputation forever when your domain is young. This is because - buying new domains and sending SPAM over that is a typical signature of an email spammer. So, spam filters are extra cautious about you in your early days.

If you have maintained a good email behavior for years it is hard to damage your reputation until something really tragic (like a phishing attack) happens using your domain.

47).  Sending a lot of emails in a very short period of time on a new domain

This is a typical signature of a Spammer. Also, a new domain (read: business) cannot build a big email list organically overnight. So, if you try sending, say, a million emails over a brand new domain, most of them will go right into SPAM + the domain reputation will take a hit.

48). Frequent changes in the email sending domain

This behavior again mimics the signature of a Spammer. If your older domains have a poor reputation they have high reason to believe that you will continue that behavior with the name domain as well.

Email Engagement

Email providers don't talk about it openly but we have seen email engagement to be really important in getting good email opens. Also, this entire topic is contextual in nature. For example - your emails might start landing in SPAM for a user who has not interacted with your last 10 emails but for a user who has opened 3 out of last 10, the emails will still reach the inbox. But, if a majority of your users don't open your email, email providers have a strong reason to believe that the emails from this domain are no longer adding value.

Here are the behaviors that result in a bad email engagement:

49). Not cleaning your email list

There is no point sending emails to a user who does not open your email. You are not only wasting your money but also adding to a poor domain reputation. I can't recommend this enough. Whenever we onboard a new customers experiencing low opens, we recommend them to prune their email list.

From a domain reputation standpoint:

50% email opens for 5,000 subscribers (2,500) > 20% email open for 50,000 subscribers (2,500)

50). Non opt-in email list

This one should be pretty obvious by now. Apart from getting a lot of SPAM complaints and email bounce, people won't engage with your email(they don't know you... why will they?)

51). Not having a double opt-in list

What is better than a Single Opt-In(SOI) list? A double opt-in list (DOI). That said, I must point out that there are valid arguments on either side.

My point of view on this is driven by this simple logic - You don't make money from the size of your list (unless you sell email lists, which I sincerely hope is not the case), you make money when people engage with your emails. DOI leads to better engagement and hence better domain reputation.

Email list size is a vanity metric for most businesses.

Be sure about the value you want to deliver with your email marketing and test out both the SOI and DOI for that. Whichever moves the needle, go for it.

I leave it up to you to take a call on this.

Start a Free Trial
No credit card required. Instant setup.

52). Your subscribers delete your email (without reading them)

This is worse than an unread email. This tells that users are confident that they will not get any value from your email(s). Of course, there is little you can do to directly change this except to write better email copies and even better email subject lines.

In case you are stuck with email subject lines, we have created the biggest collection of best performing email subject lines here.

53). Not asking users to add/mark your email address in address book/safe sender list

This should be obvious.

SendX strongly recommends this to its users. And this step is a part of our deliverability checklist which we go through with for all customers.

Gmail subscribers should be encouraged to create a filter to ensure none of your emails ever go to SPAM. This is a really neat trick that you must follow.

Here is how you do it for all popular email clients.

54). Not segmenting the list (sending all emails to all subscribers)

This might change based on your business. If you cater to users with multiple interests it is best to segment them based on that and so that you only send relevant emails.

Segments are a combination of (and) and (or) conditions on top of your email lists.

Using segments you can hyper-target your audience.

Segmentation to hyper target audience

SendX is a has a powerful segment creator to help you do just that. We can help you segment users based on 50+ various attributes like - type of page visited, company name, demographic data such as age, gender, DOB, email opens, clicks. Know more about it by getting in touch with us.

Start a Free Trial
No credit card required. Instant setup.

55). Not sending campaigns at the right time (time zone + likeliness to open at a particular time)

Note - This is not valid for time-sensitive emails.

Everyone has a different email habit. Some process it at fixed time(s) every day, others do it more randomly.

Send emails as per user behavior
Send emails as per user behavior

The most optimum solution for an email marketer would be to  send an email right when the users is most likely to open their inbox. The email will be right at the top! Of course, this would require telepathic powers and sadly the world has not reached there yet!

Send emails by Timezone
Send Emails by Timezone

But, we have a solution for you until then. SendX has two really cool features that can probably help you come as close to it as possible.

a). Smart campaigns - With smart campaigns we send your emails at a time they are most likely to open it.

How? With time, we learn your users email open behaviour. When you send a "Smart Campaign" we use that data and send emails based on that.

b). Geo optimized delivery - This is important if you have subscribers from across the globe. Suppose you want to send a campaign at 9 AM, Geo Optimized Delivery ensures that everyone gets the email at 9 AM their local time. That's right, no more sending marketing emails to your subscribers at 2:32 AM!

56). Secondary level email engagement metric:

  • Link Clicks
  • Replies
  • Forwards
  • Multiple Email Opens

The point is simple - The more a user engages with your emails the more a SPAM filter will get confident about your domain.

Email engagement = Email providing value to recipients

Otherwise, why would they spend time engaging with it?

MailBox Usage:

We have seen Gmail being especially stringent about it. Here are few cases to be aware off:

57). No real inbox for your domain

You need to have an email inbox for your domain (which you want to use to send marketing emails). It will give you legitimacy in the email world.

Email providers and Spam filters will get to know this since your domain:

a). Might not have MX record (Mail Exchanger record) - This is a publicly available record.

b). Reply emails will bounce.

58). No inbox for a from email OR reply-to email address field

If you are sending emails using a from email address which does not have a real inbox you might be successful initially but, pretty soon you will start facing issues. Email providers and SPAM filters will know this is an invalid email once your receipts try to reply (email replies will bounce).

This is the same reason it better to never use a <no-reply>@ email address in your "from" OR "reply-to" email address.

Remember this: Say No to No Reply.

59). Very Low Mailbox Usage

There are two problems here:

a). This is typical behavior of a sophisticated spammer.

b). This is never a behavior of a real business. Ever heard of a business that sends a lot of marketing emails but doesn't use emails regularly to run their business?

Other Factors

60). Inconsistent domains for from email & reply-to address

Email header has an option for you to explicitly set an email address that will get auto-filled when the recipients click on the reply (email) button. This helps in cases where you want all the replies of your email campaign to be diverted to a specific address (like - support@ or marketing@). Just be sure that your From Email domain and reply-to email domain are same.

At SendX, we have seen emails that were landing in SPAM started going to the Inbox after changing this very thing.

61). Very frequently changing IPs

IP/Infrastructure Reputation refers to the backend infrastructure which is used to send emails. This is taken care by the ESP you are using to send an email. Very Frequently Changing IPs for your email is typical behavior of a Spammer (as they keep trying new IPs for better delivery).

62). The domain used for phishing attacks

This can happen if your domain got compromised by hackers. The domain used to do the attack will get blacklisted pretty quickly.

C). IP/Infrastructure Reputation:

IP/Infrastructure Reputation refers to the backend infrastructure which is used to send emails. As a marketer or an email user you never interact with it directly.

Taking our finance world analogy of credit score to the next level: if domain reputation was the credit score for your email domain then IP reputation is the credit score for the IP (email server). Again, a lot like domain, it takes time to build an IP's reputation.

In order to know the reputation of an IP you should check its Sender Score. Anything above 90 is a healthy score. Sender Score is a comprehensive reputation measurement covering email senders worldwide.

You need to decide on what IP infrastructure should be sending emails - shared or dedicated based on your business requirements.

Shared IP vs Dedicated IP
Shared IP Vs Dedicated IP

Here are the pros & cons of both the choices:

a). Dedicated IP

This is best when you are sending a consistently high volume of emails. Dedicated IP will be used exclusively to send your campaigns only.

It helps you built a reputation over a period of time. It allows you to be in total control over your email deliverability.

On the flip side, inconsistent sending pattern or dips & spikes in email sends may lead you being classified as a spammer.

If you are sending more than 200k emails on a consistent basis then opting for dedicated IP will be the better choice.

SendX offers dedicate IP services to its users.

Start a Free Trial
No credit card required. Instant setup.

b). Shared IP

This works well when you are just getting started with building an email list.

On a shared IP pool, you will have many businesses sending from the same IP.

Why do SPAM filters and Firewalls consider the reputation of the IP at all? This is required to ensure anyone who provides email infrastructure has skin in the game in keeping the email traffic clean.

An IPs reputation takes a hit whenever unsolicited emails of any kind are sent over it. So, email infrastructure providers have to ensure they do not allow Spammers over their infrastructure.

Since an IP's reputation is so much dependent on the kind of emails that get sent over it so, a lot of reasons that affect the domain's reputation also affect its IP.

Here are some factors that affect IP Reputation.

63). IP not warmed up properly

IP warm-up is a process to establish a reputation for a new IP. Or an IP that has not been used for some time. This also makes it difficult to send a lot of emails over a new infrastructure. A lot of ESPs do not warm-up their IPs correctly which leads to poor deliverability for their users. If you are facing such issues there is little you can do about it apart from requesting your ESP to move you to a different IP or switch to a new ESP.

64). IP Server not configured properly

If the backend of the ESP is not configured with proper email header, authentication parameters, and encryption then the emails will get rejected by Email providers (like Gmail, Yahoo Mail, AOL etc.)

65). IP Present in Blacklists

Just like domain blacklists, there are IP blacklists as well. If an IP gets blacklisted all emails going over that IP will take a hit.

Here is a way to check if your IP is in any blacklist.

Here are few guides to read if your IP is present in Gmail’s Blacklist, Hotmail/Outlook’s Blacklist and Yahoo!’s Blacklist.

We proactively help our users and help them get delisted from these blacklists. Do reach out to us for more help in this regard.

66). Not having TLS Authentication

Email runs over the top of a protocol called SMTP (Simple Mail Transfer Protocol) which is unencrypted by its very nature. TLS or transport level security provides a mechanism to encrypt email messages which prevent the content being read from entities other than the intended recipients.

You can check this using the email headers when you receive them. If your ESP is not using TLS authentication for their IPs, it will affect their reputation.

67). Inconsistent Email Volume over the IP

If your IP is sending 10,000 emails one day and 500k emails on the second day then there is something wrong. The IP you are using should be sending consistent email volume to maintain its reputation.

Sudden changes in email volume are always looked at suspiciously by the SPAM filters.

68). IP not having Return Path Certificate

Return Path is a company that provides data and insights to help organizations optimize their email marketing. They also provide certificates (to ESPs) that is used as a signal of better authority by major email providers. Check more details.

69). IP used for phishing attacks

If the IP has been used for phishing attack its reputation will drop overnight and you can know that by seeing the drop in its Sender Score. You should move to another IP in such a case.

Here are other reasons which lead to poor IP reputation. These are same as what effects the domain as well, so I won't get into details:

70). Purchased email list

A purchased list will take a hit on your IP reputation due to reasons already discussed in the Domain Reputation section. It could be either you or other senders who are sending emails over the IP you are using.

71). Users marking emails going over the IP as SPAM

This is the most common reason for the IP losing its reputation. If you are on shared IP, then someone else spamming can make a part of your emails go to SPAM as well.

72). Email sent over the IP getting bounced

Just like a domain, an IP will lose its reputation if consistently a high percentage (> 5%) of emails sent over it is bouncing.

73). SPAM trap emails present in the emails going over the IP(s).

As I have already covered, SPAM trap emails are like the secret agents of SPAM filters. Just like in case of domain reputation, your IP reputation will take a beating if a lot of SPAM trap emails are present in the emails going over the IP. This is an indication for Spam filters that the ISP is allowing bad email traffic over its infrastructure.

74). Emails sent to a non opt-in email list(s)

Non opt-in email list means that the email user present in the list did not give consent to receive (marketing and sales) email from the respective business. This is the definition of a SPAM email. Hence a non opt-in list is looked down upon by SPAM filters. How do they know it is a non opt-in list? The email recipients will mark the email as SPAM and it is highly likely that the list will have higher than usual bounce and SPAM trap emails.

75). Sending a lot of emails in a very short period of time on a new domain

This has a direct impact on the domain reputation but also expect your IP reputation to take a hit too since it is regularly allowing this behavior. As mentioned before, the email gatekeeper penalizes the email infrastructure for even allowing such spammy behavior over there IPs.

76). Not having an inbox for domains which are sending an email over the IP

All sending domains over an IP need to have an email inbox for their domain.

Spam filters will get to know this since the domain:

a). Might not have MX record (Mail Exchanger record). This is a publicly available record.

b). Reply emails will bounce.

You will start seeing a hit to your IP reputation if this happening regularly.

77). Not having an inbox for a "from email" OR "reply-to" email address that is used while sending the email over the IP

Now, there could be a scenario when the domain has inbox BUT the "from email" being used while sending the email does not. A common example of this is <no-reply>@ email addresses.

SPAM filters will know this is an invalid email once your receipts try to reply (because the reply emails will bounce).

You will start seeing a hit to your IP reputation if this happening regularly.

If a portion of your email traffic is landing in SPAM then you are leaving money on the table.

A portion of your prospects and users are not getting important messages from you like: pricing changes, deal emails, new features, and product updates, upgrade opportunities and a host of other things.

Your revenue is leaking because your emails are landing in SPAM.

But, understanding why your emails are landing in SPAM could be really complicated.

With this guide, we have attempted to lay down all that LAWS that govern the SPAM world.

So, that you are no longer part of the collateral damage in a war being waged against email SPAM.

SendX complies with all the above laws.

Start a Free Trial
No credit card required. Instant setup.

In case your emails are landing in SPAM and you are struggling to figuref it out all by your self, reach out to us for help.

Don't leave money on the table, fix your revenue leakage now.


1). What exactly is a spam email?
Spam email is any unsolicited email, which is usually sent out in bulk, and which is irrelevant, annoying and sometimes malicious. A few examples are fake lottery win announcements, get rich quick schemes, and fake job schemes.

2). Why do emails go to spam?
Common reason for emails going to spam are listed as below:

  • Spam trigger keywords in the body
  • Spammy subject lines
  • Absence of unsubscribe link
  • Unsafe attachments
  • Poorly written copy

3). How can I ensure that my emails don’t go to spam?
In order to ensure that your emails don’t go to spam, you need to adhere to certain rules such as the ones listed below:

  • Send only to opted-in subscribers
  • Explicitly ask subscribers to whitelist your email address
  • Comply with anti-spam laws
  • Proofread your emails to avoid spelling & grammar errors
  • Avoid spam-trigger keywords
  • Send them to a cleaned up list
  • Include an unsubscribe link

There are quite a few more such rules for this. You can find an extensive list here.

4). How can I know if my emails have gone to spam?
There is actually no way to know whether your email landed in a specific contact’s inbox or SPAM folder once it got delivered. It could have been sent to SPAM by the contact’s email service provider, or the recipient could have manually reported as SPAM, etc.

5). What happens to my sender reputation when my emails go to spam?
If your emails are regularly marked as spam by the recipients, your domain reputation will deteriorate. And based on that, email service providers may automatically send your emails directly to spam.

6). What are the common spammer-behaviors which I can avoid?
Common spammer-behaviors which need to be avoided to ensure that emails don’t land into the spam box are: bad spelling and grammar, image-only emails, and spammy subject lines containing words like “free”, “$$$”, “unlimited” etc.