550 5.7.520: External forwarding not allowed (Microsoft 365)
A forwarding rule tried to send your mail to an outside address, and the organization's security policy blocks that.
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 5.7.520 Access denied, Your organization does not allow external forwarding. Please contact your administrator for further assistance.Common causes
- A personal rule forwarding work mail to Gmail or another outside account
- Microsoft 365's default outbound spam policy, which blocks automatic external forwarding
How to fix it if you sent the email
- Remove the forwarding rule, or ask IT whether forwarding to that address can be allowed.
If you manage the receiving or sending mail system
- Allow forwarding for specific users in the outbound spam filter policy, if your policy permits 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 5.7.520 mean?
- A forwarding rule tried to send your mail to an outside address, and the organization's security policy blocks that.
- Is 550 5.7.520 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 5.7.520 bounce?
- No. Fix how the mail is sent; the address itself is probably fine.