A copy pasted into a tester is not the email your recipients get. They get the one Gmail sends: through Google's servers, signed by your domain or by Google, with whatever your signature and your links add. The add-on checks that email, because it puts our test address into the same send.
How it works
- Open a new email in Gmail and click the Email Spam Tester icon at the bottom of the compose window.
- Press Add test address to Bcc. Recipients cannot see a Bcc address, so this works on a real email to real people as well as on a test.
- Send. Then open Email Spam Tester in the side panel on the right: the test is at the top of your recent tests, and the report is usually ready about a minute after the email arrives.
In the panel you get the score, a What to fix list with only the checks that failed or warned, and a Fix plan whose DNS records sit in fields you can copy from. Open full report opens the same test on this site, where every check is listed with the RFC section behind it.
To check something you send from somewhere else, such as a newsletter platform or your own server, press Get a test address in the side panel and send the email to that address from there.
Which folder it lands in
Under Where does it land? in the compose window, a second button also adds inboxes at Gmail, Outlook, Yahoo and other providers, and the report then shows where each of them filed the email: inbox, promotions or spam. Those inboxes find the test by a short marker at the end of the subject, so the add-on asks you for the subject and writes it back with the marker. Use this on a test copy and not on an email to real people. Some of those inboxes are public test inboxes, so leave confidential content out.
What it can see
The add-on cannot read your mailbox, your contacts or the text of any email. In the draft that is open it can see the To, Cc and Bcc addresses, and nothing else. It needs the Bcc list because setting Bcc replaces it: the addresses already there go back in next to ours. The draft changes only when you press one of the add-on's buttons, which adds the test addresses and, for the folder check, sets the subject. It also connects to email-spam-tester.com and to no other service. Your recent tests are kept by the service under a random id the add-on creates for your Google account. Your name and email address are not used for this. The details are in the privacy policy.
If you already have an API key from the Zapier or n8n page, you can link it under Settings in the add-on. After that the key's limits apply, and your Gmail tests stay with the key on any Google account you link it on.
Somewhere other than Gmail
Mail that never passes through Gmail can be tested from the home page: send it to the address you get there. The Chrome extension keeps that address one click away, and the API hands it to scripts.