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The role of email service providers in deliverability
Priya NainJun 9, 2023 2:07:24 AM7 min read

The Role of Email Service Providers in Deliverability

You often spend hours crafting the perfect email campaign. You obsessively refine every sentence, pick the ideal images, and you're convinced this is the message that will finally capture your audience's hearts and wallets.

You hit 'send'... and then you wait. And wait.

But your open rate is as dismal as a rainy Monday.

You might have faced this situation a number of times.

Now, you might be thinking, "I've done my part! I've created engaging content, I've segmented my audience, and heck, I even tested my email before sending it out. Why aren't my emails reaching my audience?"

Sometimes, the issue is beyond the confines of your beautifully designed email and its compelling content. It lies hidden in the corners of the world of email deliverability.

This is where Email Service Providers (ESPs) step in. They can play a crucial role in your email deliverability, ensuring your painstakingly-crafted messages don't end up banished to the digital oblivion of a spam folder. Let's explore the role of Email Service Providers in email deliverability.

What are ESPs?

An Email Service Provider (ESP) is a company that offers services related to emails. These services can be varied and might include email creation, email sending, email management, and email delivery to a list of subscribers. A well known ESP is They help you create, send, and track high volume emails without losing them in the spam folder.

Don't confuse delivery and deliverability

First of all, let's clarify two terms that are often confused.

Delivery rate is the percentage of the number of emails delivered divided by the number of emails sent. Deliverability is where your message lands if your subscriber does receive your email.

If it lands in the spam folder, that means there is low deliverability although the message has been delivered.

How does an ESP affect your email deliverability

1) Infrastructure maintenance

The infrastructure of an ESP comprises the technical elements needed to send and deliver emails. At the core of this infrastructure is the Simple Mail Transfer Protocol (SMTP) server, which is essentially the backbone of all email delivery.

ESPs also interact with Internet Service Providers (ISPs). Each ISP has different rules and algorithms for handling incoming emails, including factors like spam detection and filtering. The ESP maintains relationships with these ISPs and adapts to their rules to ensure that the emails they send on behalf of their clients are delivered successfully in the inbox.

2) Sender Reputation Management

Sender reputation is a score assigned to an organization that sends emails. This score is used by ISPs to determine whether to deliver emails to the recipient's inbox, send them to the spam folder, or block them entirely.

Factors contributing to the sender's reputation include the volume of emails sent, the number of spam complaints, bounce rates, and the number of emails sent to non-existent addresses.

ESPs help manage the sender's reputation by monitoring these metrics and advising their clients on best practices.

For example, they might advise a client to purge non-responding addresses from their email list to reduce the bounce rate. They might also provide tools for handling feedback loops with ISPs, which allow the sender to see when recipients have marked their emails as spam and adjust their approach accordingly.

3) Email Authentication

Email authentication is a method used to verify that an email has actually come from the domain it purports to have come from. This helps protect against phishing and spoofing attacks, where an attacker might try to make an email appear as if it has come from a reputable source.

There are several protocols used for email authentication:

  • SPF (Sender Policy Framework): SPF allows the owner of a domain to specify which mail servers they use to send mail from that domain. When an email is received, the recipient's mail server can check the SPF record of the domain in the email 'from' address to see if the server that sent the email is authorized.
  • DKIM (DomainKeys Identified Mail): DKIM adds a digital signature to the headers of an email. This signature can be checked by the recipient's mail server to verify that the email was indeed sent by the domain it claims to come from and that it hasn't been tampered with during transit.
  • DMARC (Domain-based Message Authentication, Reporting & Conformance): DMARC is a policy that allows a domain owner to indicate that their emails are protected by SPF and/or DKIM. It also tells the recipient's mail server what to do if neither of those authentication methods passes – such as sending the email to the spam folder or rejecting it outright.

The ESP helps implement these authentication protocols by providing the necessary tools and instructions, making it easier for the sender to authenticate their emails and improve their deliverability.

4) Bounce Management

Emails can 'bounce' for several reasons, such as when the recipient's mailbox is full, the server is down, or the email address doesn't exist. ESPs provide tools to manage these bounced emails.

They track and classify them as either a hard bounce (an email that is rejected due to a permanent reason, like a non-existent email address) or a soft bounce (an email that is rejected due to a temporary issue, like a full mailbox).

It's crucial to remove hard bounces from your list to maintain your sender reputation.

5) List Segmentation

ESPs also offer tools to segment your email list. Segmentation involves dividing your list into smaller groups based on criteria such as customer behavior, demographics, or past purchases.

This enables more personalized and targeted emails, which can lead to higher engagement and better deliverability.

6) Deliverability Reporting

ESPs offer comprehensive reporting tools to provide insights into your email campaign's performance. These include:

  1. Open Rate: This is the percentage of recipients who open your email. A low open rate might suggest that your subject lines aren't compelling or your emails are landing in the spam folder.
  2. Click-Through Rate: This is the percentage of recipients who click on a link in your email. A low click-through rate might suggest that your email content isn't compelling or relevant to the recipient.
  3. Bounce Rate: This is the percentage of emails that were not delivered successfully. A high bounce rate can harm your sender reputation.
  4. Delivery Rate: This is the percentage of emails that were successfully delivered to the recipient's server. If this rate is low, it might suggest issues with your email list or sender reputation.

Through these reports, senders can identify issues affecting their email deliverability and make necessary adjustments to improve their email campaigns.

7) Content Analysis and Spam Testing

ESPs provide tools to analyze the content of your emails to see if they contain elements often associated with spam. For instance, the ESP might flag emails with excessive use of all caps, excessive use of exclamation marks, or words often associated with spammy content.

They can predict whether it will land in the inbox or spam folder and provide a 'spam score' based on various factors. This gives you an opportunity to make changes before sending your email to the actual recipient list, improving your chances of avoiding the spam folder.

8) Unsubscription management

Unsubscription management plays a crucial role in the overall email deliverability process, and ESPs (Email Service Providers) are instrumental in ensuring that this process is handled smoothly and effectively.

ESPs typically provide built-in features that allow businesses to include an unsubscribe link in their email campaigns. This link is strategically placed, often in the footer of the email, making it easily visible and accessible to recipients.

Upon confirmation of the unsubscription request, the ESP takes immediate action to remove the email address from the sender's mailing list. This step is crucial in maintaining a clean and up-to-date subscriber list. ESPs handle the technical aspects of removing the email address, ensuring that the recipient no longer receives emails from that sender

Choosing an an ESP that aligns with your email deliverability needs

Here are seven questions to ask from an ESP when choosing one for high email deliverability:

  1. What is your average inbox placement rate?
  2. Do you provide dedicated IP addresses or shared IP pools?
  3. How do you prevent spam complaints?
  4. Do you support email authentication protocols (SPF, DKIM, DMARC)?
  5. What deliverability tracking and reporting features do you offer?
  6. How do you handle deliverability issues or blacklisting?
  7. What deliverability-related support and resources do you provide to clients?


By entrusting deliverability to ESPs, businesses can focus on crafting engaging content while leveraging the expertise and technology of these providers to maintain a positive sender reputation and reach the inbox of their subscribers effectively.

Remember that email deliverability is not enough to have a profitable email marketing strategy. You also need to deliver value and foster engagement. So, as you choose an ESP and refine your email strategy, consider how you can consistently deliver relevant and engaging messages that resonate with your subscribers, ultimately driving business growth and customer loyalty.



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.