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553 5.1.2: Recipient domain not found

The part after the @ isn't a domain that can receive mail: it doesn't exist, or has a typo.

Bounce type
Hard bounce (permanent)
What to do
Suppress the address
Returned by
Gmail / Google Workspace; Any mail server

What 553 5.1.2 means

5.1.2 is 'Bad destination system address': the domain part of the address (right of the @) doesn't exist or can't accept mail. Gmail returns 553 5.1.2 'We weren't able to find the recipient domain' when you send through Gmail to such an address.

Unlike 5.1.1, the whole domain is the problem, so every address at that domain will fail.

What the bounce looks like

The wording providers document for this code. Your bounce may add an IP address, a session ID or a help link after it.

Gmail
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.

Why cold emailers see 553 5.1.2

  • Typos in the domain (gmial.com, company.co instead of company.com).
  • A company that rebranded, was acquired, or shut down and let the domain lapse.
  • Trailing punctuation or spaces in the address from bad CSV parsing.
  • A domain with no MX or A record, or a null MX that explicitly says it accepts no mail.

How to fix 553 5.1.2

  1. Suppress the address and check whether other contacts on the same domain are in your list.
  2. Trim whitespace and punctuation from addresses when importing.
  3. Run an MX lookup on your lead domains before a campaign; any domain without working MX records should be dropped.

Retry or suppress?

Suppress. Retrying won't help unless the domain comes back.

Reading the code

The basic code 553 means "Mailbox name not allowed (permanent)" under RFC 5321. In 5.1.2, the 5 is the class (permanent failure) and the 1 is the subject (addressing). The detail number 2 is registered in RFC 3463 / the IANA registry as "Bad destination system address".

Class 5
Permanent failure
Resending the same message won't work. Something about the message, the recipient or the sender has to change first.
Subject 1
Addressing
A problem with the sender's or recipient's address: syntax or validity.
Detail 5.1.2
Bad destination system address

Check the rest of your setup

Paste the headers of a message that did get through into the email header analyzer to confirm SPF, DKIM and DMARC pass, and check your domain with the SPF, DKIM & DMARC checker. The deliverability checklist covers the rest of a healthy sending setup.

Got a different bounce? Paste it into the SMTP error code lookup to decode it.

FAQ

Is 553 5.1.2 a hard bounce or a soft bounce?

553 5.1.2 is a permanent failure (a hard bounce): the receiving server won't accept this message if you send it again unchanged. Here the problem is the address itself.

Should I remove the contact after a 553 5.1.2 bounce?

Yes. Suppress. Retrying won't help unless the domain comes back.

What does 5.1.2 mean in the error code?

In 5.1.2, the 5 is the class (permanent failure) and the 1 is the subject (addressing). The detail number 2 is registered in RFC 3463 / the IANA registry as "Bad destination system address".

Related SMTP codes

See all SMTP error codes

Sources

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Clement reads the bounces that land in your Gmail and SMTP inboxes and tells dead addresses apart from policy blocks: it suppresses the first across every campaign and keeps the contact on the second, so you don't have to decode bounces by hand.

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