GMX, WEB.DE and mail.com · permanent error
550: recipient domain does not exist
The domain in the recipient address did not exist in DNS when GMX tried to deliver (NXDOMAIN), so the message could not be delivered.
- GMX, WEB.DE
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550
- Provider
- GMX, WEB.DE and mail.com
- Temporary or permanent
- PermanentRefused for good: the message comes back to the sender, and resending it gets the same answer.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
550 Requested action not taken: mailbox unavailable
What it means
Case r1701 means GMX looked up the MX records of the recipient domain given in RCPT TO and got NXDOMAIN: the domain did not exist at the time of the attempt. That is usually a typo in the domain, or a domain that has expired or been deleted. The reply is permanent. GMX says the person responsible for the domain has to make sure an MX record exists, and suggests contacting the recipient by other means if the error persists.
Common causes
- The recipient domain is misspelled.
- The domain expired or was deleted from its registry.
- The domain is new and its DNS was not yet published.
How to fix it
- 01Check the spelling of the domain in the recipient address.
- 02Look the domain up in DNS to see whether it exists.
- 03Contact the recipient another way to get a working address.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
Related codes
- 451Temporary DNS error during the MX lookup.GMX could not complete the MX lookup for the sender or recipient domain because of a temporary DNS error, so it deferred the message.
- 550Recipient domain has no valid MX or A record.The recipient's domain is not set up in DNS as the RFCs require, with an MX record whose host has a valid A record, so GMX refused the mail.
- 550Mailbox unavailable.The receiving server permanently refused the message for this recipient: the mailbox does not exist, cannot be reached, or the server rejected the message by policy.
550 at other providers
- 550 [SC-001]Outlook.com policy block for content or reputation.Outlook.com rejected the mail for policy reasons tied to spam-like content or to the reputation of the sending IP or domain.
- 550 [SC-002]Outlook.com block for namespace mining.Outlook.com blocked the sending IP because it behaved like a namespace miner, checking whether addresses exist without sending mail.
- 550 [SC-003]Outlook.com block for an open proxy or relay.Outlook.com rejected the mail because the sending IP appears to be an open proxy or open relay.
- 550 [SC-004]Outlook.com block after complaints.Outlook.com placed a block on the sending IP because it received complaints about mail coming from it.
- 550 [DY-001]Outlook.com refuses dynamic IP addresses.Outlook.com rejected the mail because the sending IP is dynamic address space, which it generally does not accept mail from.
- 550 [DY-002]Outlook.com block for a likely compromised sender.Outlook.com rejected the mail because the sending server or computer appears to be compromised or infected.
Further reading
All 57 GMX, WEB.DE codesEvery code in the wikiPaste your own bounce