What 550 5.7.1 means
The message Gmail attaches to this code is “This message is likely unsolicited email.”, as written on its reference page. The first digit says how final it is: a 5xx reply is permanent for that message, so the sending server gives up and returns a bounce. The enhanced status 5.7.1 says what class of problem it is: content. The receiver classified the message as spam on its content, usually together with reputation.
Why it happens
The receiver scored the message itself and did not like it: the words, the links, the ratio of image to text, a link shortener, a tracking domain with no reputation of its own, or an attachment type it distrusts. Content verdicts lean on the sender's standing, so the same message from an established domain often gets through.
What to do first: Gmail classified the message as spam on content and reputation together. Score the content with the template analyzer, check the domain's tier in Postmaster Tools, warm.
Where warming fits
550 5.7.1 in this form is Gmail judging the sender's standing, and standing is built on engagement over time. Fix anything structural first (authentication, blacklists, list quality), cut the volume so the pattern stops, then rebuild the reputation the way it is earned: real engagement from real mailboxes over a ramp. That is what warming does, and a placement test shows when it has worked.
How to fix it, in order
- Score the message with the template analyzer
- Check the domain's reputation; content verdicts lean on it
- Warm the mailbox so the same content lands
Related codes
- 550 5.7.1 (Gmail): rate limited
- 550 5.7.1 (Gmail): policy prohibits the email
- 550 5.7.1 (Gmail): IP not authorized to send directly
- 550 5.7.1 (Gmail): very low sending domain reputation
- 550 5.7.1 (Microsoft): unable to relay
More on Gmail
- Google Workspace emails going to spam: the Postmaster-led diagnosis, dashboard by dashboard
- Gmail and Yahoo bulk sender requirements: the rules behind Google's authentication and spam-rate rejections
- Google Workspace email warmup: the ramp against Google's own sending limits
- Emails suddenly going to spam: the six changes behind a sudden drop, and how to confirm each
Questions about 550 5.7.1
What does 550 5.7.1 mean?
Gmail returns 550 5.7.1 with the message "This message is likely unsolicited email.": likely unsolicited email. The receiver classified the message as spam on its content, usually together with reputation.
Is 550 5.7.1 a hard bounce or a soft bounce?
A hard bounce for that message: the 550 reply is permanent, and the message is not retried. Whether the address should be removed depends on the cause: here the fix is on the sending side, not the list.
How do I fix 550 5.7.1?
Gmail classified the message as spam on content and reputation together. Score the content with the template analyzer, check the domain's tier in Postmaster Tools, warm. Gmail's own reference for the code is linked on this page.
Does email warmup fix 550 5.7.1?
It is part of the fix. 550 5.7.1 in this form is about the sender's reputation with Gmail, and reputation is built through engagement over time, which is what warming supplies. Fix authentication and list problems first, then warm.