MailFixIt

SMTP destination error

SMTP 550 5.1.2: Bad destination system address

The receiving system says the destination domain is invalid or cannot be routed. This usually concerns the domain after @ in the recipient address.

Problem description

The registered response text is:

550 5.1.2 Bad destination system address

Run this automated test on my domain

Enter your domain. MailFixIt checks the relevant DNS records automatically and shows the evidence.
Is this temporary or permanent?

SMTP 550 is permanent for this attempt. Retry only after correcting the address or destination route.

Fix the destination

  1. Copy the rejected recipient address from the full bounce.
  2. Check the spelling of the domain after @. Remove spaces or punctuation.
  3. If the address is correct, check that the recipient domain exists and has a valid MX route.
  4. If the domain publishes Null MX, it intentionally does not accept email.
  5. If you do not manage the recipient domain, send the bounce to the recipient through another channel.
  6. Retry only after the address or route changes.

Do not change sender authentication

SPF, DKIM, and DMARC on the sender domain do not repair a bad destination system address.

Frequently asked questions

Which domain should I check?

Check the domain after @ in the rejected recipient address, not the sender domain.

Can the sender fix this?

The sender can correct a typo. The recipient domain owner or mail provider must repair DNS or routing.

Related email diagnostics

DNS record not detected after saving the provider-issued valueDiagnose a DNS record that is not detected after saving it. Compare the exact TXT, CNAME or MX value, identify a duplicated hostname, and avoid unsafe DNS changes. Email delivery delayed or rejected after a DNS migrationDiagnose email that stopped arriving after a DNS change. Compare public MX records with the intended provider and avoid false alarms for mail gateways. SMTP 5.1.8: Bad sender's system addressDiagnose SMTP 5.1.8 when the sender's domain or system address cannot be resolved or accepted.

Primary sources: IANA SMTP Enhanced Status Codes, RFC 3463: Enhanced Mail System Status Codes.