550 5.1.2 Recipient domain not found

  • Permanent: the sender won't retry
  • Senders often stop emailing the address

What the message looks like

  • 550 5.1.2 Host unknown
  • 550 5.1.2 Bad destination system address
  • 550 5.1.2 Domain not found

What it means

The domain after the @ couldn't receive the email. Either it doesn't exist, or it has no working mail server. The standard name for this status is "bad destination system address".

Unlike 550 5.1.1, which means the mailbox is missing, this means the whole domain can't take mail.

Common causes

  • A typo in the domain, such as gmial.com or outlok.com.
  • The domain has expired or was never registered.
  • The domain exists but its MX records are missing or point to a server that doesn't exist.
  • The domain was moved to a new email provider and its DNS hasn't been set up yet.

If you're the recipient

Check the domain in the address you gave out. If it's your own domain, check it hasn't expired and that its MX records point to your current email provider. DNS changes can take a few hours to reach everyone.

If you're the sender

Check the address for typos first, as that's the most common cause. If the domain looks right, look up its MX records with a DNS tool. If there are none, nothing will reach it until the domain owner fixes it.

If you use addy.io

If you use your own domain with addy.io and senders get this error, check the domain's MX records match the ones shown on your Domains page, and that the domain hasn't expired. See verifying your domain's DNS records.

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