550 5.7.708: Traffic not accepted from this IP (Microsoft 365)
Microsoft is refusing outgoing mail from this IP because of low reputation. It usually affects new or trial Microsoft 365 organizations sending through Microsoft's own servers.
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 5.7.708 Service unavailable. Access denied, traffic not accepted from this IP.Common causes
- A new or trial Microsoft 365 tenant
- A sudden burst of email from a new organization
- A compromised account sending spam
How to fix it if you sent the email
- Tell your IT admin or email provider.
- Check for hacked accounts sending spam.
If you manage the receiving or sending mail system
- Contact Microsoft Support with the full bounce message and ask for help with the sending IP.
- Review outbound spam reports and secure any compromised accounts.
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 5.7.708 mean?
- Microsoft is refusing outgoing mail from this IP because of low reputation. It usually affects new or trial Microsoft 365 organizations sending through Microsoft's own servers.
- Is 550 5.7.708 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 5.7.708 bounce?
- No. Fix how the mail is sent; the address itself is probably fine.