450: mailbox 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.
- GMX, WEB.DE
- Provider
- Temporary (4xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 450
- Provider
- GMX, WEB.DE and mail.com
- Temporary or permanent
- TemporaryThe sending server keeps the message and tries again later.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
450 Requested mail action not taken: mailbox unavailable
What it means
Case r1602 is the temporary counterpart of case r1601. The recipient mailbox exists but cannot take mail right now, so GMX answers with a 450 and your server keeps the message. Mail servers repeat such attempts several times over a period before giving up. The case page gives no reason for the unavailability and asks nothing of the sender beyond letting the retries run. If the condition continues for longer, GMX suggests contacting the recipient by other means.
Common causes
- A temporary state of the recipient mailbox on the GMX side.
- GMX gives no reason on the case page, so the cause is not visible to the sender.
How to fix it
- 01Let your server retry on its normal schedule.
- 02If the message is still undelivered when your server gives up, contact the recipient another way.
- 03Do not remove the address from your list for a single 450; act on repeated permanent failures instead.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
Related codes
- 550Mailbox 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.
- 450Recipient is receiving too fast.GMX deferred mail to one recipient because it was being sent too often or with too many parallel attempts. It will be accepted on a later retry.
- 450Mailbox temporarily unavailable.The server did not take the message for this mailbox for now, because the mailbox is busy or temporarily blocked by policy. The sending server will try again.
450 at other providers
Further reading
All 57 GMX, WEB.DE codesEvery code in the wikiPaste your own bounce