How to use Google Postmaster Tools for deliverability monitoring

If you want to improve your deliverability and email marketing performance, you have to track, measure, and optimize your emails.

Monitoring key deliverability metrics is important because it allows you to react to things that can impact your email deliverability, like a high spam complaint rate.

Higher email deliverability = more people reached = higher ROI on your emails.

One of the essential tools in email deliverability is Google Postmaster Tools. It contains data straight from Gmail, making it the most accurate source for metrics like complaint rates.

What is Google Postmaster Tools?

Google Postmaster Tools is a free tool from Google that gives you access to your email performance and reputation data. Their data includes gmail.com, googlemail.com, and paid Google Workspace addresses.

It’s worth signing up even if Gmail isn’t your primary target. Understanding how Google perceives your emails can help you understand how other ISPs like Microsoft see them.

For privacy reasons, data will only show if you’re sending enough emails to Google inboxes. Google doesn’t publish the threshold, but it seems to be upwards of around 300 emails per day to Google recipients.

How to sign up for Google Postmaster Tools

To use Google Postmaster Tools, you’ll first need a Google account.

Then, Sign up or log in to Google Postmaster with your Google account. After selecting Get Started, you’ll be asked to add your domain.

Select Next, and you’ll be asked to verify your domain ownership.

Log into your DNS provider (like GoDaddy or Namecheap) and add the TXT record provided, then go back to Google Postmaster and click on Verify. Once the record is properly published and Google can find it, you’ll see the domain status change to Verified.

That’s it. Don’t later remove the DNS record you added, or you’ll lose the verification status.

Google Postmaster Tools deliverability metrics to monitor (and how)

To get started with deliverability monitoring, you’ll need to track these:

• Spam complaint rate
• IP reputation
• Domain reputation
• Authentication success rate
• Delivery errors

Spam complaint rate

The spam rate is the percentage of emails marked as spam by users versus emails sent to the inbox. This metric becomes even more important in 2024 when Google starts to require a spam rate of less than 0.3%.

While useful, the spam rate doesn’t provide the full picture. That’s because it specifically refers to spam complaints. You could see a low spam rate even if your emails are being delivered directly to spam — people can’t complain about your emails if they don’t see them.

IP reputation

IP reputation is how emails originating from your sending IP are perceived. A higher IP reputation means emails from this IP are more likely to reach inboxes. A low IP reputation can result in your emails being sent directly to spam.

Google Postmaster Tools splits IP reputation into four categories. The definition of spam here includes email reported by users as spam (this is the spam complaints metric mentioned above) and email detected by Gmail’s spam filter.  

• Bad: A history of sending a high volume of spam. Mail from this IP will almost always be rejected or marked as spam.
• Low: Known to send a considerable volume of spam. Mail from this IP will likely be marked as spam.
• Medium/Fair: Known to send good email, but has occasionally sent a low volume of spam. Most email from this IP will have a fair deliverability rate unless there’s a significant increase in spam levels.
• High: A good track record of a very low spam rate, and complies with Gmail’s sender guidelines. Mail will rarely be marked by the spam filter.

If you’re using a shared IP address like most people, your IP reputation is also shared among everyone sending from that IP. That’s why it’s important to pick a reputable email service provider that doesn’t allow spammers.

Domain reputation

Like IP reputation, domain reputation is how emails from your sending domain are perceived.

• Bad: A history of sending a high volume of spam. Mail from this domain will almost always be rejected or marked as spam.
• Low: Known to send a considerable volume of spam. Mail from this domain will likely be marked as spam.
• Medium/Fair: Known to send good email, but has occasionally sent a low volume of spam. Most email from this domain will have a fair deliverability rate unless there’s a significant increase in spam levels.
• High: A good track record of a very low spam rate, and complies with Gmail’s sender guidelines. Mail will rarely be marked by the spam filter.

Domain reputation within GPT refers only to the domain you use to send emails, like acme.com or newsletters.acme.com. However, though individual subdomains carry their own reputation, they do also share in the reputational pool of the primary domain and other subdomains so it is a good idea to make sure all are reported on.

Authentication success rate

Email authentication refers to your SPF, DKIM, and DMARC. Properly authenticated emails is an indicator of non-spam email, and in 2024 DMARC compliance is required by Google.

A high authentication success rate means your emails are secured and passing authentication tests, which can help improve deliverability.

Google Postmaster Tools shows the percentage of emails that passed SPF, DKIM, and DMARC over all received emails that attempted authentication.

• SPF graph: the percentage of emails that passed SPF versus all email from your domain that attempted SPF.
• DKIM graph: the percentage of emails that passed DKIM versus all email from your domain that attempted DKIM.
• DMARC graph: the percentage of emails that passed DMARC alignment versus all email received from your domain that passed either SPF or DKIM.
  

Delivery errors

Delivery errors tell you why your emails aren’t being delivered. Google Postmaster Tools shows what percentage of your total emails were rejected or temporarily failed as compared to all authentic traffic.

• Rate limit exceeded: your domain or IP is sending at a suspiciously high rate and you’ve been temporarily limited.
• Suspected spam: your email is suspected to be spam by Google.
• Email content is possibly spammy: your email is suspected to be spam, but specifically because of its content. In this case, you can use SendForensics to analyze your email content for spam triggers.
• Bad or unsupported attachment: your email contains attachments not supported by Gmail, like .bat or .exe.
• DMARC policy of the sender domain: your DMARC policy is reject and this email failed DMARC.
• Sending IP has a low reputation: your IP reputation is very low.
• Sending domain has a low reputation: your domain reputation is very low.
• IP is in one or more public RBLs: your IP is listed on a real-time blackhole list.
• Domain is in one or more public RBLS: your domain is listed on a real-time blackhole list.
• Bad or missing PTR record: your IP is missing a DNS pointer (PTR) record.

Ideally you won’t run into any delivery errors — but if you do, this is a starting point for troubleshooting.  You can then use a tool like SendForensics to analyze the emails for the source of these issues.

Encryption

The encryption dashboard shows what percentage of your inbound and outbound traffic is TLS encrypted.

If your email system is set up for TLS, it will attempt to negotiate TLS encryption with every server you send to or receive from. Emails sent using a non-TLS connection to an account that’s expecting encryption will likely be rejected.

Your encryption pass rate should always be 100%. If it isn’t, contact your email service provider.

Feedback Loop (FBL)

There’s another graph Google Postmaster Tools offers: the feedback loop. ISPs use feedback loops to tell senders about spam complaints.

Gmail’s feedback loop is only available to email service providers. It’s an aggregated FBL, so reports are rolled up into identifiers you define in the Feedback-ID header.

If you’re not an ESP, you can’t access this data.

Final thoughts

Sender reputation is a core part of email deliverability. There’s a lot you can do with GPT, but there’s some parts of deliverability monitoring only premium deliverability tools can do:

• Deliverability analysis. A premium deliverability tool analyzes your entire email and sending infrastructure for problems. Optimizing emails is easier when you can see what content looks spammy, and you can troubleshoot delivery errors like missing PTR records.
• DMARC monitoring. With a platform like SendForensics’ DMARC monitoring, you can troubleshoot emails that failed DMARC tests and see how to fix it.
• Alerts. Google Postmaster Tools doesn’t let you know if there’s a problem. Platforms like SendForensics monitor your GPT data in the background and send you notifications when there’s a reputation issue.

SendForensics integrates directly with Google Postmaster Tools. See your GPT data directly in SendForensics next to other reputation signals like campaign performance, and use alerts to monitor your reputation and get notified when something goes wrong.