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Guaranteed email deliverability
Priya NainJun 27, 2020 12:00:00 AM9 min read

100% Inbox Deliverability: Truth & Proven Tips

Morty was a beginner in email marketing. His browser history never had an entry about email deliverability. All of his focus was on dashing templates or quirky subject lines.

Then Morty saw a drop in his open rates, click rate. Upon reading more about it on our blogs, he discovered the cause to be the low email deliverability.

He locked himself in a room with 20 Red Bulls and desperately tried to find an ESP promising 100% email deliverability.




He came out with a tattoo on his arm - ‘there ain’t no thing like 100% deliverability.’

That’s how we got the idea of writing this blog so that no one else has to get a tattoo or ingest sugared flavory water only to find that there is nothing like guaranteed inbox delivery.

When someone or an ESP promises an inbox guarantee, they mean that 100% of your emails will land into the inbox. It can be any tab - promotional, updates, or even primary but no email will crash land into the spam folder.

But all factors don’t depend on someone or an ESP so they can’t actually deliver on the promise of 100% deliverability. So don’t trust such claims.


Don't trust 100% deliverability claims. (via GIPHY)


Let’s understand that the major Inbox service providers want to protect their users and their servers from hackers, and ‘extra-smart’ spammers. So they invest heavily in blocking any email that might fit their category of being spam. And it even depends on the receiver. What might be spam for you, might not be spam for me.
Even if you have a highly engaged list, enviable sender’s reputation that webs trust with all kinds of authentication, you can’t get 100% deliverability.


Because these spam filter algorithms are not perfect. They will sometimes send a legitimate email to the spam folder and spam to your inbox. And they are constantly learning new patterns and changing the old ones.

Your problem is worse when you are sending high volume emails to a cold list. (A cold list is a list of qualified prospects who have no prior relation to you.) They can be easily converted to hot leads if you manage to convince them about the benefits of your products or service.

But of course, they should first be able to receive an email from you in their inbox.
So let’s focus on getting the tools & information you need to achieve maximum deliverability and not waste time by aiming for a unicorn to fart rainbows… yeah, I mean not waste time going after 100% deliverability.

The best part is that this information is super useful even if you have a cold email list.

To understand the impact of poor email deliverability, just think of what all can go wrong in the real life when emails don't reach the subscribers or land in the spam folder:

  • Important communications are lost
  • Hassles with transactions, like order confirmation
  • Missing out on customized deals and offers
  • Abandoned carts remain the way they are
  • Networking opportunities are missed

You can avoid all this and more, by implementing the best practices and tips covered in this blog.

But pause for a second to understand what email deliverability is:

Email deliverability is the measurement to see if your email will land in the subscriber’s inbox or not. Since the email servers don’t inform the sender in which section of the receiver’s mailbox did the email reach (spam or the inbox), calculating email deliverability becomes crucial to anticipate campaign performance.

Phew..!! Now that that definition is clear, let's dive right in!

Choose an ESP with deliverability as one of its core focus

Most of the deliverability depends on the sender, but for infrastructure, technical stuff you can look towards your ESP.

Choose an ESP that follows these best practices:

  • Warm-up their shared IP pools.
  • Ask users to use their own sending domain.
  • Isolate users that have low deliverability into separate IP pools so that the ones with good deliverability are not affected.
  • Give you data on email metrics to judge how good or bad the email deliverability is.

Actively monitor their ecosystem, adhere to best email practices, and get rid of foul users.
If you want an ESP that can get close to perfect, I would suggest you check SendX, which boasts of 90%+ deliverability for its customers. Many known brands shifted to SendX after failing to improve deliverability rates on other platforms and are committing to long term relationships.

You can check the features, usability, and deliverability by signing up for a free trial for 14 days. Requires no credit card. Signup here.

Clean up your list

Remove any invalid, inactive, spam traps, or catch-all email addresses.

Doing that will give you two major benefits:

  • You will avoid being marked as a spammer as you will be sure that you are sending emails to a valid list with the actual email addresses.
  • Data quality is another factor inbox service providers look at when determining what to do with your emails. If a list doesn’t have invalid data, and engagement is strong, your emails are more likely to reach the inbox.

You can use an online service to do so. They provide 99% accuracy. Check out the list here.

Let them unsubscribe

When you send an email to the whole list, there are high chances you will experience a wave of unsubscribers.

Unsubscribe option

But it’s not always a bad thing. It’s better to have a highly engaged list rather than just a vanity metric of a large number of a ‘not interested’ public.

Some important tips:

  • Put your unsubscribe link in the footer - that’s a standard place where everyone looks for it.
  • Don’t hide it in long sentences or images.
  • Don’t make anyone log in to their account or reply to you to unsubscribe. Enable one-click or maximum two-clicks to unsubscribe.
  • Of course, ensure that your unsubscribe link is not throwing a 404 or 500 error (duh).
Easy-to-find unsubscribe link

Unsubscribe link in the footer can be as simple as what is used by Email Mastery emails… Just a word & one-click step to unsubscribe.

Without an unsubscribe link, you will have a large number of people reporting spam. A high volume of email combined with a surge in spam complaints will send a negative signal to spam filters and that will degrade your deliverability further.

Avoid spammy words in subject lines

Certain words or combinations of words can trigger spam filters and your emails will crash land  into the spam folder.

Spam filters are smart and are always weeding out subject lines that say ‘earn $10000 in 10 days’ or ‘100% guarantee weight loss without exercise’.

Here are some tips to keep your subject lines clean:

  • Don’t use ‘too-good-to-be-true’ subject lines
  • Avoid spammy words that are used to make claims or outrageous offers like ‘100% off’, ‘free’, ‘$$$’, ‘chance’, ‘password, ‘guarantee’. There is a long list of these words you can easily find here
  • Don’t write subject lines with exclamation marks or capitalized words. PEOPLE DON’T LIKE TO BE SCREAMED AT!. I am sure you got my point ;)

Another reason why you should have crisp, honest, and engaging subject lines is so that people open your emails.

Since ISPs(Internet Service Providers) are taking note of all variables, including the engagement from the recipients, a good subject line will give you plus points with the ISP and it will allow your email to land safely in the inbox.

Here’s a genius and foolproof tip one of my mentors taught me:

“If you want to create your own list of 'spammy subject lines’  and actively avoid them, you can check your own spam box. Then think if what you are writing belongs there or in the actual inbox. Then tweak accordingly.”

Avoid spammy subject lines

Follow content best practices

  • Use correct spelling and grammar. Take time to edit and proofread. You can use services like Grammarly to help you with that.
  • Link only to genuine sites with reputable domains.
  • Avoid shortening your links when you hyperlink a text, button, or image.
  • Don’t write long emails that feel like a novel. Spammers tend to write long emails with obfuscated links so it’s suggested to avoid lengthy emails.

Don’t send image-only emails

Email clients can’t read images. They can only parse your text. Hence using image-only emails is a notorious technique used by spammers to hide their text.

So when you exhibit the same behavior as a spammer, your emails won’t pass the check of spam filters and hence won’t make it to your reader’s inbox.

If you ever wished that you had beautiful templates where you could put your text and don’t have to create heavy images ever again, you are at the right place. Because I am gonna suggest you try the ever-expanding template library offered by SendX.

Avoid sending image-only emails

You can check out the whole library, easy to use editor, and get access to millions of stock images even when you just try SendX for free for the first 14 days. No credit cards or lists or email requests required.

Wrap Up

Deliverability is damn confusing & also very unsexy. But once you set up a good strategy and set guidelines according to best Email practices we just listed, you will be able to achieve deliverability & hence ROI that will be enough to justify all the efforts of email marketing.

If you wish to take on understanding the underworld of email deliverability & solve your problems all at once, you can download this ‘Email Deliverability - The Definitive Guide [Updated 2024]’..



1) How is email deliverability calculated?

Email deliverability is the measure of how many emails land into the inboxes of your subscribers. It is often expressed a percentage and can be calculated like this:
Email deliverability = (Emails that went into inbox/Total Emails Sent)*100

2) What is a good email deliverability rate?

Generally, 95% and higher is regarded as a good email delivery rate for any ESP. This means that for every 100 emails sent, at least 95 should have been delivered.

3) What are some factors that affect email deliverability?

Some factors that affect email deliverability are:

  • The volume of emails you send
  • The frequency with which you send your campaigns
  • Open rate, click-rate, and unsubscribe rate
  • Bounce rate or emails which go undelivered.

4) How can I improve email deliverability?

You can improve email deliverability by ensuring that you maintain a clean list, writing a good subject line, writing content that will pass the spam filter's checks, avoiding using image-only emails, including an unsubscribe link, using a legitimate 'From' or 'reply-to' address, and maintaining a good IP reputation.


Priya Nain

A writer, content marketer, and editor with 4+ years of experience helping SaaS companies get users, and engage them. Nice girl, rarely mean.