ISP Deliverability Guide: Gmail (Updated for 2024)

Google's Gmail might be the preeminent mailbox provider. Launched in 2004, Gmail has grown from the "new kid on the block" into one of the biggest hosts of individual email mailboxes in the world. Depending on what data you look at, you might even see Gmail as the #1 mailbox provider, at least here in the US.

Gmail's spam filtering systems incorporate user feedback and engagement. And they know what they're doing. If you are not sending wanted mail to people who requested that mail and who read that mail at high enough percentages, you're going to struggle. You won't reliably get your mail to the inbox. Their systems are too good -- their magic spam fighting robots look at metrics very closely -- and their view of certain metrics can even change over time! What got you to the inbox in 2019 might not be good enough to get you to the inbox in 2024. Deliverability success at Gmail requires not only that you adhere to best practices, but it also necessitates ongoing monitoring and tweaking of your marketing program.

Spam Resource Top Five Deliverability Tips for Gmail:

  1. DO enable email authentication: SPF, DKIM and DMARC. Sender Policy Framework (SPF) is a simple DNS record that conveys what IP addresses are allowed to transmit mail for your domain. It's easy to configure and there's absolutely no reason you shouldn’t have already implemented SPF. Domain Keys Identified Mail (DKIM) is a little bit trickier. Your (or your ESP’s) outbound mail server needs to support DKIM directly; it involves signing outbound mail with a cryptographic key. You don’t see a message’s signature by default; it’s stored in a hidden header. But the receiving ISP (in this case, Gmail) uses that to ensure that the mail was truly from the domain name it claims to be from. DMARC is a domain policy for how mailbox providers should handle un-authenticated mail, and at Gmail, sender implementation of DMARC was upgraded from a "recommended best practice" to a requirement, in 2024. Find more on DMARC and email authentication here.
  2. DO enable TLS. Back in 2015, Google warned that they were going to eventually highlight mail sent over unencrypted SMTP connections. They started doing so in 2016, adding a scary "unlocked" icon to messages sent over SMTP connections that don't utilize Transport Layer Security. The reality of the situation is that Google is pushing email senders to make it harder for bad guys and governments to monitor email in transit. This is another "strongly recommended" best practice that was upgraded to a documented requirement in 2024.
  3. DON'T focus on "Promotions" vs "Updates" tab placement. Google wants to place marketing mail in the "Promotions" tab and trying to outsmart them is not something you'll get away with in the long term. Instead of spending effort on an arms race of trying to outsmart shifting Gmail filters, focus on sending wanted mail and subscribers are going to read it regardless of what tab it shows up in. (And keep in mind, whichever tab it is under, it is actually in the inbox.)
  4. DON'T buy or rent lists. Google is very sensitive to feedback from Gmail subscribers. Send mail to a purchased list, and enough people will mark that mail as spam, and Gmail's filters will pick up on that and then all your mail goes to spam. Cleaning up after you fall into this trap takes time and is not fun. As of 2024, Gmail suggests keeping spam complaints below .1% and warns that above .3%, blocking is quite possible.
  5. DO focus on engagement. Gmail's filtering is heavily engagement-driven. (You will occasionally find a marketer who swears otherwise, but they're full of beans. I am not.) If you're struggling to get solid inbox placement, a common fix is to adjust who you're sending to so that you are mailing only subscribers who have opened or clicked in the past 9-12 months. Stick to that for at least 30 days, and that will likely result in you getting solid inbox placement, and should keep your mail out of the spam folder. (If your mail truly is wanted by your subscribers.) Then you have to decide what to do about the rest of your subscriber base, the people who aren't responding. Sunsetting, for example.
I've got a whole Yahoo Mail & Gmail Sender Compliance Guide that you'll want to check out. It goes over the new 2024 requirements in detail with guidance on how to comply with each of the documented requirements.
DON'T look to a technological solution to fix a permission problem. Almost all of the time, the reason a sender's mail is going to the spam folder is because that sender didn't fully follow best practices. There isn't some a header or code you need to add that will fix a deliverability problem caused by low engagement or a lack of permission. Sure, occasionally an ESP or email platform will mess something up, and you should definitely work with them to check to see that SPF, DKIM, bounce processing, and all that other stuff are working properly (see Gmail's Sender Guidelines to learn more). But let's be clear -- it is rare that a technical failure is the source of a deliverability issue.

Contacting Google for Help

Google does have a remediation request submission process (click here), where you can go and submit a sample message, state your case, and request that they reconsider spam folder placement (or blocking) of your messages. Use it. But only AFTER you're sure that you're doing everything right. If you're buying lists or trying to email people who haven't responded in years, you're wasting your time. But if you ARE doing everything right, and you think Google is unfairly filtering your messages, they do offer this review process.

Historically, they don't usually respond to these submission requests (though they suggest that this may change in 2024). However, they do review each submission and sometimes do make spam filtering tweaks if your submission was compelling or if it reveals an issue that they feel merits addressing. Make the submission and continue to monitor deliverability. They warn that, even if they do take your concern seriously and make adjustments to address your issue, it could take two weeks for you to notice any changes in your ability to deliver mail to the inbox.

Google Postmaster Tools

Google has a reputation portal called Google Postmaster Tools (GPT). Register your domains here and you'll get some varying level of information about your domain and IP reputation and in some instances, this will help you identify problems that need your attention. Not always -- the data can occasionally be a bit cryptic -- but it is what it is and you should check it out to see what benefit you can glean from it. Here you'll find Google's support page for GPT.

Deliverability Evolves Over Time

Google tweaks their spam filters over time, resulting in new error messages, new reasons for deferrals, and new explanations around how best to comply with ever-evolving best practice requirements. If you want to stay on top of all of this, sign up for the Spam Resource newsletter, where I share stuff like this often.

Click here to view the whole series of Spam Resource ISP Deliverability Guides.
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