550 5.7.133: Group only accepts internal senders (Microsoft 365)
You emailed a group or distribution list that only accepts messages from people inside the organization.
Blocked The address is probably fine. The problem is how the mail was sent.
What the bounce message looks like
The wording changes from one provider to another. These are typical examples:
550 5.7.133 RESOLVER.RST.SenderNotAuthenticatedForGroup; authentication required; Delivery restriction check failed because the sender was not authenticated when sending to this groupCommon causes
- The group is set to block outside senders, which is often the default
How to fix it if you sent the email
- Email a person in the organization directly, or ask them to let outside senders reach the group.
If you manage the receiving or sending mail system
- In the group's settings, allow people outside the organization to send to it.
Free tool: paste the full bounce into the bounce message decoder to get a plain-English reading of every code in it.
Questions people ask
- What does 550 5.7.133 mean?
- You emailed a group or distribution list that only accepts messages from people inside the organization.
- Is 550 5.7.133 a hard or soft bounce?
- Blocked. The address is probably fine. The problem is how the mail was sent.
- Should I remove the address after a 5.7.133 bounce?
- No. Fix how the mail is sent; the address itself is probably fine.