What 550 5.1.1 means
The message Gmail attaches to this code is “The email account that you tried to reach does not exist.”, 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 5.1.1 says what class of problem it is: recipient problem. The recipient address does not exist, is inactive or is full. A list-quality problem; a rising rate of these damages reputation.
Why it happens
The address does not exist, has been deactivated, or the mailbox is full. Usually it is list quality: an old export, a typo, a role address that was retired, or a spam trap sitting in a bought list. A few are unavoidable, but a rising share tells the receiver the sender does not know who it is mailing.
What to do first: Invalid address. Verify lists; a rising 5.1.1 rate damages reputation.
Why warming does not fix this
Warming builds sender reputation. 550 5.1.1 in this form is a recipient problem problem, and no amount of engagement history changes it. Fix the cause and the bounce stops; warming is for what comes after, when the mail is accepted and the question becomes which folder it lands in. See how warming works for that part.
How to fix it, in order
- Remove the address; a rising rate of these lowers reputation
- Verify the list before the next send
- Watch the bounce rate in the sequencer and in Postmaster Tools
Related codes
- 550 5.2.1 (Gmail): account is inactive
- 552 5.2.2 (Gmail): inbox out of storage and inactive
- 452 4.2.2 (Gmail): recipient inbox out of storage
- 550 5.4.1 (Microsoft): recipient address rejected
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 Postmaster Tools domain reputation: what the reputation tiers and the spam rate mean
Questions about 550 5.1.1
What does 550 5.1.1 mean?
Gmail returns 550 5.1.1 with the message "The email account that you tried to reach does not exist.": account does not exist. The recipient address does not exist, is inactive or is full. A list-quality problem; a rising rate of these damages reputation.
Is 550 5.1.1 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 it should.
How do I fix 550 5.1.1?
Invalid address. Verify lists; a rising 5.1.1 rate damages reputation. Gmail's own reference for the code is linked on this page.
Does email warmup fix 550 5.1.1?
No. 550 5.1.1 in this form is a recipient problem problem, and warming builds reputation, which is not what is failing here. Fix the cause and the bounce stops.