SMTP 553 5.1.2
recipient domain not found
SMTP 553 5.1.2 means the domain in the recipient address does not exist or cannot accept mail. RFC 3463 defines X.1.2 as "bad destination system address". Gmail returns it as "We weren't able to find the recipient domain." Every address on that domain will fail, so remove it.
Should you remove the address?
Remove the address from your list
Yes, unless you can correct a typo in the domain. A domain with no mail server cannot receive anything, so the address is dead as written.
Hard bounce. Do not retry. It will fail every time.
How it appears
553 5.1.2 We weren't able to find the recipient domain. Please check for any spelling errors, and make sure you didn't enter any spaces, periods, or other punctuation after the recipient's email address.
550 5.1.2 Host unknown (Name server: example.com: host not found)
What causes it
- A typo in the domain, such as gmial.com or a missing letter in a company domain.
- The domain has expired or was never registered.
- The domain exists but has no MX or A record, so mail has nowhere to go.
How to fix it
In order — try the first one first.
- Check the domain for an obvious typo and correct it if you can confirm the right address.
- Look up the domain's MX records. If there are none, no address there can receive mail.
- Remove the address. Retrying a domain that does not exist will not work.
Who sends it
Gmail returns 553 5.1.2 when you send from a Gmail or Workspace account to a domain it can't find. Other sending servers report the same situation as "Host or domain name not found".
Gmail
Reply text We weren't able to find the recipient domain.
Gmail goes on to ask you to check for spelling errors and stray spaces or punctuation after the address.
Common questions
- What does SMTP 553 5.1.2 mean?
- SMTP 553 5.1.2 means the domain in the recipient address does not exist or cannot accept mail. RFC 3463 defines X.1.2 as "bad destination system address". Gmail returns it as "We weren't able to find the recipient domain." Every address on that domain will fail, so remove it.
- Should I retry a 553 5.1.2 error?
- No. 553 is a permanent failure, so the message will never be delivered no matter how many times you try. Remove the address — repeated sends to permanent failures are one of the main signals mailbox providers use to throttle a sender.
- How do I fix SMTP 553 5.1.2?
- Check the domain for an obvious typo and correct it if you can confirm the right address.
- Is 553 5.1.2 a hard bounce or a soft bounce?
- 553 5.1.2 is a hard bounce. The receiving side has said the address can't receive mail, so a retry won't deliver it. Do not retry. It will fail every time.
- Should I remove the address after a 553 5.1.2 bounce?
- Yes, unless you can correct a typo in the domain. A domain with no mail server cannot receive anything, so the address is dead as written.
- Will verifying my list prevent 553 5.1.2?
- Yes. A mailbox check asks the recipient's server whether the address exists without sending anything, so addresses that would return this code are flagged before the send instead of bouncing against your domain.
Clean the list before the next send.
A bounce report only tells you about the addresses you already mailed. The rest of the list has the same kinds of dead mailboxes in it, and each one becomes a hard bounce recorded against your domain the moment you send.
- A real SMTP mailbox check on every row, before anything is sent
- Dead and mistyped addresses split out, so they never reach your sending tool
- Catch-all, disposable and role addresses flagged alongside
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Other 553 replies
Sources
- Source: Google Workspace Admin Help: Gmail SMTP errors and codes
- Source: RFC 3463: Enhanced Mail System Status Codes
Provider wording is quoted only where the provider publishes it.
Last reviewed 2026-10-22