550: domain record allows no senders (Sender ID)
Outlook.com refused the mail because the sending domain publishes a record saying no server may send for it, such as v=spf1 -all.
- Microsoft
- Provider
- Permanent (5xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 550
- 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 command rejected due to Sender ID validation failure
What it means
Outlook.com will not deliver mail from a domain whose owner has published a Sender ID record that allows no IP at all to send, for example the TXT record v=spf1 -all. Domains that never send mail use that record to protect themselves from spoofing. If such a domain is later used for email, the record still tells Outlook.com that every sender is unauthorized, and it answers with 550 command rejected due to Sender ID validation failure. Microsoft notes that changes to the record can take up to 48 hours to propagate.
Common causes
- The domain publishes v=spf1 -all because it was once set up not to send mail.
- The domain began sending without its record being updated.
How to fix it
- 01Look up the domain's SPF record.
- 02Replace the record with one that lists the servers and services that send for the domain.
- 03Wait up to 48 hours for the change to propagate, and test before resuming normal sending.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- Outlook.com Postmaster: Troubleshooting (SMTP error codes)substrate.office.com
Related codes
- 550 5.7.23SPF violation on outgoing mail.The destination checked SPF on mail sent from your Microsoft 365 organization and rejected it, which points to a problem in your SPF setup.
- 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
- 550Refused for a header or address problem.Yahoo or AOL refused the message for a policy reason tied to its headers, its addresses or the sending domain's DNS. Yahoo lists these as other policy errors, sent as 550 or 554.
- 550Not an Xfinity customer.The address you sent to does not belong to an Xfinity customer. The failure is permanent, and Xfinity asks bulk mailers to treat it as an unsubscribe.
- 550Too many invalid recipients.Xfinity refused the whole message because too many of its recipients were invalid, so nobody received it. Clean the recipient list and send it again.
- 550Sender domain has no A or MX record.Xfinity refused the message because the domain you send from has neither an A record nor an MX record in DNS. Add one and send again.
- 550Account not available.The Xfinity account you wrote to is currently not available. Xfinity sends this as a 550, so the message has failed, though the account itself may come back.
- 550Permanent reject under an exceptional blocklist.GMX permanently refused mail from your system because it is on one of the blocklists GMX uses in exceptional situations. The message comes back and is not retried.
Further reading
All 111 Microsoft codesEvery code in the wikiPaste your own bounce