Bounce codes › Microsoft 365
550 5.7.520: Your organization does not allow external forwarding
A mailbox in Microsoft 365 tried to forward a message automatically to an address outside its organisation, and the organisation's outbound spam policy forbids that.
Only the recipient side can fix it Refused by a rule on the recipient side
Your own organisation blocks automatic forwarding to outside addresses.
- Sent by: Microsoft 365 / Outlook
- Permanent (hard bounce). Sending the same message again fails again.
How Microsoft 365 words it (source):
Access denied, Your organization does not allow external forwarding.
Why it happens
- A user set up automatic forwarding to a private Gmail or other outside address.
- An inbox rule forwards or redirects certain mail outside.
- Microsoft 365 blocks automatic external forwarding by default.
What to do
- If you set up the forwarding: ask your administrator whether it can be allowed for your mailbox.
- Administrators: the setting is "Automatic forwarding rules" in the outbound spam filter policy of Microsoft Defender.
- If you did not set up any forwarding, tell your administrator: unknown forwarding rules are a common sign of a hacked mailbox.
Don't confuse it with
The person who gets this bounce is the original sender, but the message did reach the first mailbox. Only the automatic copy to the outside address was blocked.
Questions
I am an outside sender and got this. Did my email arrive?
It reached the mailbox you wrote to. Its automatic forward to another address failed.
Should I remove the address?
No. The address works.
Got a different bounce?
Paste the whole message into the bounce code lookup. It reads the code and the words and tells you whose move it is.
Related codes
550 5.7.133Sender not authenticated for group (Microsoft 365)