Gmail 550 5.7.1: message is likely unsolicited mail
550 5.7.1Message likely unsolicited mailPermanent: retrying will not helpFrom Gmail and Google Workspace
550-5.7.1 [203.0.113.40] Our system has detected that this message is likely unsolicited mail. To reduce the amount of spam sent to Gmail, this message has been blocked. - gsmtp
What it means
Here Gmail’s spam classifier decided the individual message is spam and refused it outright, rather than delivering it to the Spam folder. The verdict blends content, links, sender reputation, and how similar mail has been received by Gmail users. It is a permanent 5xx response, so the specific message will not be retried.
Compare it with the reputation flavour of 5.7.1, which blames the IP or domain itself, and with 4.7.28, which slows you down instead of rejecting. This text points at the message. A different message from the same server might well get through, which is a useful test.
Likely causes
- Links to domains or URL shorteners that Gmail associates with phishing or spam campaigns.
- Cold outreach or purchased list mail that many recipients have marked as spam in the past.
- Content heavy on images, very little text, or wording typical of scams and lottery notices.
- A forwarded message that originally came from a spammy source, now relayed through your server.
How to fix it
- Send a plain, short test from the same server to a Gmail address you control. If it lands, the problem is the content or links in the bounced message.
- Strip or replace every link, especially shorteners and tracking domains, then retest one change at a time.
- Make sure the message is something the recipient asked for, includes a working unsubscribe, and comes from a consistent From address.
- Review Postmaster Tools for a spike in user spam reports around the time of the bounce.
Checks that apply
- Email Deliverability Reviews the sending domain for common spam signals before you resend.
- Email Header Analyzer Shows the authentication results and relay path, so you can rule out forwarding or a failed signature.
- Blacklist Check Checks the domains in your links and your IP against DNSBLs that Gmail’s signals often agree with.
FAQ
- Will resending the same email work?
- Usually not. Gmail scores the content again and reaches the same verdict, so change the message or its links first.
- Can the recipient do anything?
- A Workspace admin can add an approved sender list or a spam bypass rule for your domain. A personal Gmail user has no setting that overrides an SMTP rejection.