550: mailbox does not exist or is disabled
The GMX, WEB.DE or mail.com address you wrote to does not exist, was disabled after a long period without use, or was blocked by the provider.
- 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 r1601 is the GMX hard bounce for the recipient. GMX gives three reasons it may apply: the address does not exist on its systems, the owner has not used the mailbox for an extended period so it was temporarily disabled for inactivity, or the address was blocked for administrative reasons. The bounce does not say which one applies. For a sender the result is the same: the message was not delivered and will not be. Check the spelling, and if it is right, reach the person another way. Repeated mail to such addresses also counts against you (case r0902).
Common causes
- A typo in the address, such as a missing letter or a wrong domain ending.
- The mailbox was closed or never existed.
- The owner stopped using it and GMX disabled it for inactivity.
- GMX blocked the address for administrative reasons.
How to fix it
- 01Check the spelling of the address, including the domain.
- 02If you send to a list, remove the address so it is not tried again.
- 03Contact the recipient by other means to get a current 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
- 450Mailbox temporarily unavailable.The GMX mailbox is unavailable at the moment, so the message was deferred. Your server will retry several times; if it lasts, reach the recipient another way.
- 421Too many mails to addresses that do not exist.GMX is turning your server away for a while because it sent too much mail to GMX addresses that do not exist. Clean the list before sending again.
- 550Mailbox unavailable.The IONOS-hosted address you wrote to no longer exists, or the mailbox was temporarily deactivated after a long period without use.
- 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