Email provider · 5.x.x permanent failure
Every SMTP 550 response on record from Web.de, with the verbatim text, the enhanced status code, a severity rating and a plain-English fix.
The mailbox is unavailable and the message is rejected for good. This is the catch-all permanent failure, covering everything from an unknown address to an authentication failure to a reputation block, so the wording after the number is what actually tells you the reason.
smtp;550 <[email protected]>: Reject due to SPF policy. The originating IP of the message is not permitted by the domain owner
The sending IP is not listed in the SPF record for the Return-Path domain. Add every server you send from to that record and wait for DNS to update before resending.
Provider documentation
smtp;550 <[email protected]>: Syntax error in parameters or arguments
The receiver refused this message outright and will not accept an unchanged retry. The wording above is the only clue to what needs to change, most often the address, authentication, or sending reputation.
Provider documentation
smtp;550 <[email protected]>: Requested action not taken: mailbox unavailable
The address does not exist, or is no longer active, at this provider. Remove it from your list and check for a typo in the local part or the domain.
Provider documentation
smtp;550 <[email protected]>: Bad DNS PTR resource record
The receiver could not match your sending IP to a valid PTR (reverse DNS) record, or your HELO name does not resolve. Set forward-confirmed reverse DNS for every sending IP.
Provider documentation
smtp;550 <[email protected]>: Reject due to policy restrictions (header based)
The receiver rejected the message under a policy rule rather than a content or reputation score. This is usually set by the recipient's mail admin, so ask the recipient to allowlist your sending address or domain.
Provider documentation
smtp;550 <[email protected]>: Reject due to policy restrictions (domain based)
The receiver rejected the message under a policy rule rather than a content or reputation score. This is usually set by the recipient's mail admin, so ask the recipient to allowlist your sending address or domain.
Provider documentation
smtp;550 <[email protected]>: Reject due to policy restrictions (IP based)
The receiver rejected the message under a policy rule rather than a content or reputation score. This is usually set by the recipient's mail admin, so ask the recipient to allowlist your sending address or domain.
Provider documentation
smtp;550 <[email protected]>: Requested mail action aborted: exceeded storage allocation, Quota exceeded
The recipient's mailbox is full or over its storage limit. There is nothing to fix on the sending side; delivery may succeed later once they clear space.
Provider documentation
smtp;550 <[email protected]>: IP address is block listed
The sending IP or domain is on a blocklist the receiver checks, so mail stays refused until the listing clears. Find which list flagged you, fix the underlying cause, then request removal. Delivery can stay blocked for up to a day after delisting while caches refresh.
Provider documentation
smtp;550 <[email protected]>: Invalid DNS MX or A/AAAA resource record
The receiver refused this message outright and will not accept an unchanged retry. The wording above is the only clue to what needs to change, most often the address, authentication, or sending reputation.
Provider documentation
Postmaster & documentation
The mailbox is unavailable and the message is rejected for good. This is the catch-all permanent failure, covering everything from an unknown address to an authentication failure to a reputation block, so the wording after the number is what actually tells you the reason. At Web.de, it is a permanent rejection, and the specific reason is in the enhanced status code and message text of each response below.
Match your bounce text to one of the responses below and follow its guidance. Recipient-side wording means fix the address. Authentication or reputation wording (SPF, DKIM, DMARC, blocklist) means fix your sending setup, and check Web.de's postmaster documentation.
