Google Postmaster Tools: The Simplified Explanation

Google Postmaster Tools: The Simplified Explanation


Gmail recently announced that they have around 1 billion active users - which means that a large percentage of your email marketing campaigns are destined for Gmail inboxes! And while email marketers have spent years trying to figure out how some of their campaigns go straight to the inbox and others end up in the Spam folder, Google has always kept their highly sophisticated email filtering and spam detection algorithms a closely guarded secret.

But last year Google Postmaster Tools was launched, and now email marketers finally have a window into what works for Gmail and what doesn’t. Using 7 different dashboards, qualified bulk senders are now able to gain better insight on what is affecting their deliverability within the Gmail network. And although the tool has been around for over a year now, many people don’t really understand the email metrics they now have access to!

So here is our simplified guide to help you get Google Postmaster Tools (GPT) setup, and understand what the different dashboards are telling you.

Getting started with Google Postmaster Tools

The very first thing you have to do before you can even think about using GPT is create a Google Apps or Gmail account. It is completely free and if you have been doing email marketing for a while now, the odds are that you already have one. But in case you don’t, here’s a link to create one now.

  1. Now you’ll need to login to your account and go to (bookmark this or add it to your App shortcuts as you’ll be using it a lot!).

  2. Then you’re going to need to click on the “+” icon to add the domain that you are sending emails from.

  3. The next screen will ask what domain you use to authenticate your emails, which might sound complicated but is actually pretty simple. According to Google an authentication domain is either the DKIM (d=) or SPF domain (Return-Path domain) that is used to authenticate your email. You can find it in the ‘Authentication Results’ header of an email that has successfully passed authentication (and was delivered to a Gmail mailbox). But all its actually asking is what comes after the ‘@’ symbol in your Sender/From address when you email your subscribers. For example, the screen shot above shows that Webroot’s authenticated domain is

  4. Next you will need to verify that the domain you listed belongs to you and is one you have access to. In other words, they’re making sure that you aren’t a spammer who has hijacked someone else’s domain!! Unfortunately, the new DMARC policies adopted by free email providers mean that you’ll no longer be able to verify domains like, or for your bulk email campaigns.

  5. You can verify that you own a domain by adding one of the following records to your DNS configuration:

  6. By adding a TXT record - if you don’t know where to find your TXT record then this page from Google Support should help you (check the step-by-step instructions for popular domain hosts as well)

  7. By adding a CNAME record - this is a guide to getting your CNAME record if you need it

  8. Lastly you will need to click ‘Verify’ and you’re all done!!

Interpreting info from your dashboards

Now you can click on your verified domain to access the 7 dashboards showing the stats Google Postmaster Tools has gathered on your campaigns. Unfortunately some of the dashboards will only show data on emails that have been authenticated by DKIM or SPF so if you’re not seeing data despite the fact that you’re sending plenty of mail then you are going to need to check your authentication settings.

One thing you do have to keep in mind is that GPT is designed for bulk senders who are sending hundreds and thousands of emails at a time (apparently thousands of emails are more likely to produce results than hundreds) So unfortunately, if you only have a small email database then this tool won’t work for you!

The Delivery Errors dashboard

This graph shows you all the mail that was rejected or temp-failed (which means your message didn’t reach a recipient so is essentially the same thing!) versus all the mail that actually delivered. In other words, this is a record of all the emails that ‘bounced’ back to you after being sent.

The most common SMTP delivery error codes will be 421 or 550 respectively but here’s a guide to what each of the errors you might see mean:

  • Rate limit exceeded_: Your domain or IP has been sending emails at a suspiciously high rate so Gmail has implemented temporary rate limits and will remove them once they’re sure you’re not sending unsolicited mail.
  • Suspected spam_: Due to a variety of reasons, Gmail suspects that you are sending spam
  • Email content is possibly spammy_: Gmail has scanned the content of your email and based on what it found, has determined that it may be spam
  • Bad or unsupported attachment_: The attachment/so on your email are not in a format that is not supported by Gmail
  • DMARC policy of the sender domain_: This means that you (the sender) have set up a DMARC rejection policy
  • Sending IP has low reputation:_ This error doesn’t really need an explanation does it?
  • IP is in one or more RBL’s_: The IP address your message from is listed on one or more public real-time blacklists. Check out our post on understanding email blacklists to find out more.
  • Bad or missing PTR record_: The PTR record (or reverse DNS record) of the IP address where your message originated is missing

The Domain Reputation and IP Reputation dashboards

These two dashboards are essentially the same and they tell you whether your reputation is Bad, Low, Medium/Fair or High. Your IP or domain reputation is determined by a number of factors but the most important one is how much of the email you’re sending is getting reported as spam.

And in case you haven’t realised it yet, the worse your reputation is, the more likely it is that your message will go straight to the Spam folder! These are just two of the thousands of signals used to determine whether your marketing message will get flagged as spam though, so don’t think a ‘High’ reputation means you’ll definitely end up in someone’s inbox!

The Authentication dashboard

This dashboard is actually a graph with three different readings that show you how much of your mail attempted and passed either SPF or DKIM authentication, as well as messages that then passed DMARC authentication (after passing SPF or DKIM authentication). These results are shown as a percentage of all the mail sent from a specific domain.

What this means is that if anyone is spoofing your email address to send (or try to send) unsolicited mail, you won’t know about it if this tool is the only one you rely on! The aim of course is to get a 100% success rate for all three types of authentication on every day that you’re sending emails. Checking the authentication header of your emails is pretty easy with Google, so always send yourself a test before launching a campaign!

The Feedback Loop dashboard

This dashboard is actually linked to a tool that Google launched a couple of years ago and is only available to senders who have undergone the slightly complicated process of implementing the Gmail Spam Feedback Loop (FBL). This tool was originally only available to certain ESP’s who used it to track which of their customers were abusing their services in order to send massive amounts of unsolicited mail to Gmail addresses.

But now that it is part of GPT, individual marketers will be able to use it to identify and track which of their email campaigns are getting a lot of spam complaints. Unlike other feedback loops that allow you to identify the actual user marking your messages as spam, the Gmail FBL only gives you an aggregate of results based on the identifiers included in your Feedback ID.

The Spam Rate dashboard

In this dashboard you will see the volume of spam complaints your email got shown as a percentage of all the emails you sent that day. So let’s say you send a marketing email to 100 people, and 40 of those people report your message as spam. That means you would have a spam rate of 40% (which is very bad for business by the way!). But this dashboard only works with DKIM authentication, so make sure it’s set up properly!

The Encryption dashboard

This dashboard has two separate graphs that keep track of TLS encrypted mail - one to show Inbound mail or mail that is sent from your domain TO Gmail, and another to show Outbound mail or mail that is sent FROM Gmail to your domain. If you send or receive any emails with a service that doesn’t use TLS then this percentage will drop. Plus nefarious parties would be able to peek at your email while it is en route to your subscribers!


As you have probably gathered by now, GPT gives you some of the most sophisticated and powerful tools you could possibly need to analyse your email campaigns and use the data you’ve gathered to avoid the Spam folder. However, despite the fact that Gmail is pretty much the centre of the email universe and many other email providers seem to follow where they lead - we feel that this tool lacks some important features.

Right now the only thing we’d really like to see is for Google Postmaster Tools to be available on a smaller scale so that businesses running smaller email campaigns and who don’t have thousands of subscribers on their email lists can also benefit from its insights. We’ve only just started using GPT though so we may discover something else we’d like to see but for now that’s pretty much it - and that’s saying something!!

If you are sending enough email to be able to leverage GPT metrics, and because Gmail often spots unwanted mail that manages to sneak past other spam filters - it is always a good idea to pay close attention to how your mails are performing within their network. Then once you’ve optimised your email campaigns to ensure you’re ending up in the inbox more often than not - you’ll probably find you land in almost every inbox out there!