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Glossary

Postmaster Tools

Postmaster Tools is a free Google service that shows a domain's owner how Gmail sees the mail it sends, including the rate at which recipients mark it as spam.

Updated · By Otman Ounana · How we research

Why it matters when you send from your own Gmail

Google asks senders to keep the spam rate reported there below 0.3%.[1] It needs a domain you own, so it does not help a sender using a plain @gmail.com address, and at low volume it may show no data at all. If you send from a Google Workspace domain, add the domain and check it now and then. A rising spam rate is the earliest warning that a campaign is aimed at the wrong people, long before replies dry up.

Example

You send 40 emails a day for three weeks from your company domain. A rate near zero in the dashboard is fine. A sudden jump after you change the list tells you to pause and look at who you are writing to.

What to do

Add your domain, verify it with the DNS record Google gives you, and look at the spam rate and authentication panels once a week. No data at low volume is normal and not a fault.

Related terms

All terms are on the glossary.

Read next

  • The 5,000-a-day bulk sender ruleWho Google counts as a bulk sender, what counts toward 5,000, why it is permanent, and the arithmetic for someone sending cold email from their own mailbox.
  • Can cold email get Gmail suspended?When Google pauses or suspends sending from a Gmail or Workspace account, for how long, and the habits that keep a mailbox used for cold email safe. Quoted from Google.
  • Warm-upWarm-up is the practice of starting with a low sending volume and raising it step by step, so mailbox providers see a steady pattern rather than a sudden burst.
  • Hard bounceA hard bounce is a permanent delivery failure, such as an address that does not exist, which the receiving server reports with a 5xx status code.

Sources

  1. Google, Email sender guidelines. “Keep spam rates reported in Postmaster Tools below 0.3%.” Read on 1 October 2026.