Email Sender and Domain Reputation

5 Ways Email Marketers Avoid Getting on a Gmail Blocklist

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In 2021, Gmail accounted for 36.5 percent of global email opens. As one of the most popular web-based mailbox providers (MBPs) in the world, it’s likely that they’re your go-to for email marketing. So, it stands to reason that the last thing you want is to end up on a Gmail blocklist.

What is a blocklist, anyway?

A blocklist is a list of IP addresses and domains that have been reported as “known” sources of spam. Although blocklists exist to promote a safe and spam-free email environment, getting added to one can feel like the kiss of death for email marketers.

There are two main types of IP address blocklists: Real-time Blocklists (RBL) and Domain Name Server Blocklists (DNSBL). These blocklists are updated in real time and ISPs and MBPs use them to see if a sender has been flagged as a spammer.

Domain blocklists, like URI Real-time Blocklists (URI DNSBL), focus on domain names. MBPs use these blocklists to analyze and check for spam domains in the main message or body of an email.

We all know that blocklists can negatively impact inbox placement rates, but by how much? What blocklists are used by different MBPs? Here’s what you need to know if you’re sending emails to Gmail users.

What blocklist(s) does Gmail use?

Although Google doesn’t publicly disclose which blocklists they use, our data shows a correlation between Gmail and the following:

  • Spamhaus’ Policy Block List (PBL) helps networks enforce their Acceptable Use Policy for dynamic and non-MTA customer IP ranges. Spamhaus indicates on its website that the PBL is not a blocklist and that it is perfectly normal for dynamic IP addresses to be listed on the PBL. Spamhaus insists that PBL listings do not prevent email sending unless your email program is not authenticating properly when it connects to the MBP or your company’s mail server, which can occur if you have not turned on Simple Mail Transfer Protocol (SMTP) Authentication.
  • The Spamhaus Block List (SBL) is a database of email addresses that Spamhaus identifies as associated with spam.
  • is Spamhaus’ exploit and botnet filter, which lists IP addresses coming from computers hijacked with illegal third-party exploits, including open proxies, worms, and viruses.
  • The Composite Blocking List (CBL) is an IP-based blocklist that appears to be utilized by Gmail.

5 reasons Gmail may be blocking your emails

There are over 300 publicly available spam blocklists. However, not all of these blocklists are created equal when it comes to their impact on your deliverability. As a result, MBPs and other filtering companies will often use a combination of publicly available blocklist data and an internal blocklist to help determine whether or not to accept an email.

That said, these are the usual reasons why senders (good or bad) may find themselves on Gmail’s blocklist:

Too many spam complaints

Spam complaints negatively impact your ability to land in a subscriber’s inbox. If Gmail accounts consistently mark your email as spam, your IP address may end up on a blocklist. To avoid this, ensure your email content is valuable, but above all, relevant to your subscribers.

Sending emails to spam traps

Sending to spam traps is a symptom of poor list acquisition and list hygiene practices. To avoid this, regularly suppress unengaged Gmail accounts. Blocklists also use spam trap addresses—which are fake email addresses (pristine traps) or inactive (recycled, unused) email addresses—to determine the quality and accuracy of your email list, so keep it clean!

Poor mailing list hygiene

Speaking of which, poor list hygiene is important to avoid. Mailing lists can become increasingly inaccurate if companies have weak permissions and/or fail to observe opt-out requests. Follow consistent list management to avoid inaccurate mailing lists.

Bulk sending

Sudden high-volume sending can also get you blocklisted if you have little to no established sender reputation. Avoid sending campaigns all at once or in quick succession if you’re sending from a new domain or IP address.

Email misconfiguration

Misconfiguration of your email infrastructure—for example, if your reverse Domain Name System doesn’t match your SMTP—can also lead to being blocklisted.

5 ways to avoid Gmail’s blocklist

Blocklist operators don’t necessarily want to blocklist legitimate senders, but their job is to protect email consumers from bad practices and fraud. If you’re not doing any of the following, you’re on a fast track to a blocklist near you.

Avoid spammy behavior

This sounds obvious, but it needs to be said. When a legitimate sender gets listed, it’s because their campaigns have the characteristics of a spammer. Heed the advice above and you should have nothing to worry about.

Pro-Tip: Google has specific best practices for pulling emails from other accounts (otherwise known as redirects). Trying to circumvent them will only get you into trouble.

SPF and DKIM alignment

SPF (Senders Policy Framework) and DKIM (DomainKeys Identified Mail) are the two most widely used email authentication protocols. They help ensure email security and fight against spoofing. Aligning SPF and DKIM not only adds an extra layer of protection to your emails but also boosts your sender reputation.

Keep good list hygiene

Keeping good list hygiene is crucial, especially if you want to avoid getting spam complaints, bouncebacks, or sending to invalid or fraudulent email addresses.

Follow Gmail’s bulk email senders guidelines

These guidelines are for anyone who sends emails to Gmail users. If you’re sending a high volume of emails, following these guidelines will ensure your messages are sent. It will also lower the chances that Gmail blocks your messages or marks them as spam.

Double opt-in

Be proactive about keeping your list clean by having subscribers opt-in at the point of acquiring their email, and again with a follow-up confirmation email.

How to run a Gmail blocklist check

Even good senders can end up on Gmail’s blocklist. If you’ve noticed a significant decrease in your email open rates, it’s time to figure out why.

  • Check your SMTP server logs for “500” errors. Per Google, “SMTP is an internet standard used by mail servers to send and receive email.” SMTP server error messages help you understand why a message wasn’t able to be sent, so if your messages are bouncing, check for an SMTP server error code––that may help you identify the problem.
  • Run a blocklist check for your IP addresses. As we mentioned before, there are hundreds of publicly available blocklists. If you’re worried, check the ones associated with Gmail and/or run your IP address through one of the top email blocklists.
  • Check your sending reputation via an email spam checker. Similarly to a blocklist checker, you can utilize a third-party tool to see if your emails are being sent straight to spam.
  • Check that your DNS records are correct and up to date. The Domain Name System (DNS) organizes and maps domains to their accompanying physical servers. This ensures that when someone types in your domain, they visit a website on the correct server. You can tap into a website that aggregates domain information (i.e., WHOIS lookup) to look up public information about your DNS.

How to request Gmail blocklist removal

If it turns out you’ve been put on Gmail’s blocklist, the first thing you should do is get to the root cause and address it. This is a key step before moving forward with a delisting request.

If you don’t take measures to fix and/or avoid making the same mistake, you’ll only get relisted, or worse––your request to be removed from said blocklist will be rejected.

Once you’ve gone over everything with a fine-tooth comb, you should be delisted within 3-5 days. If, after that, you still have issues with deliverability, it’s time to go ahead and make a formal request to Google through this form.

By this point, your responses to each prompt should be “No” (if any are “Yes”, Google will advise you to wait it out). Once you’ve sent the form, you should be delisted within a week.

Google doesn’t share any feedback in the above form or in response to your request. All you can do is monitor the situation and perform tests to see if your emails are getting through to the Gmail accounts in question.

Many blocklists have the option to request to be removed. If you’re looking to get delisted from Spamhaus, for example, simply head over to their lookup page and follow the instructions.

Final thoughts

Equipped with the tools you need to understand blocklists, you can eliminate them as a foe and increase inbox placement at MBPs like Gmail.

To take your email program to the next level (and stay a step ahead of hungry competitors), check out our all-in-one Ultimate Email Marketing Toolkit for expert guidance to master email’s latest challenges.