Microsoft 365 5.7.505
Access denied, banned recipient
Microsoft 365 5.7.505 means: access denied, banned recipient. It is a permanent failure, so do not retry it unchanged. Treat it as a hard bounce: check the address for a typo, then remove it from the list.
Microsoft 365’s exact wording
Quoted from Microsoft Learn: Email non-delivery reports and SMTP errors in Exchange Online, checked 2026-11-05. Placeholders are Microsoft 365’s own.
Provider's description
Access denied, banned recipient
Possible cause
The recipient that you're trying to contact isn't valid.
Provider's advice
If you feel this is an error, contact support.
| Who sends it | Microsoft 365, Exchange Online and Outlook.com |
|---|---|
| Basic code | Microsoft 365 lists the enhanced code only |
| Enhanced code | 5.7.505: Microsoft 365-specific, not in the IANA registry. Its subject digit puts it under 5.7.0 other or undefined security status. |
| Permanent or temporary | Permanent (5xx) |
| Verifying the list prevents it | Yes, verification catches this |
What the sender should do
Treat it as a hard bounce: check the address for a typo, then remove it from the list.
Would verifying the list have prevented Microsoft 365 5.7.505?
Yes, verification catches this
A mailbox check asks the recipient's server whether the address and domain can receive mail, without sending anything, so the address is flagged before the send instead of bouncing against your domain.
Common questions
- What does Microsoft 365 5.7.505 mean?
- Microsoft 365 5.7.505 means: access denied, banned recipient. It is a permanent failure, so do not retry it unchanged. Treat it as a hard bounce: check the address for a typo, then remove it from the list.
- Should I retry after Microsoft 365 5.7.505?
- No. It is a permanent (5xx) failure, so the same message to the same address will fail again. Fix the cause first. Treat it as a hard bounce: check the address for a typo, then remove it from the list.
- Would verifying my list have prevented Microsoft 365 5.7.505?
- Yes, verification catches this. A mailbox check asks the recipient's server whether the address and domain can receive mail, without sending anything, so the address is flagged before the send instead of bouncing against your domain.
Sources
- Microsoft Learn: Email non-delivery reports and SMTP errors in Exchange Online (checked 2026-11-05)
Registry and provider wording is quoted exactly; guidance is written by the SimpleVerifier Team.
SimpleVerifier Team · Last checked against the sources 2026-11-05