Your message wasn't delivered because the recipient's email provider rejected it.

[Renfield-64]

Our organisation uses Outlook 365 for email. Recently when some staff members send an email to our allstaff group a couple of the email addresses get rejected with the message:

Delivery has failed to these recipients or groups:

(email address of recipient here)

Your message wasn't delivered because the recipient's email provider rejected it.

 

This also happens if the sender sends directly to the email address.

 

The sender and recipients are all in the same organisation and the recipient actually receives the email!

 

I have googled this quite a bit but the answers seem to refer to people from outside of the organisation having the issue.

 

Any ideas? Do you need more info from me?

 

Thanks

[Danp]

Have they got a forwarder setup?

[Chaniel]

You'll likely need to do some more digging, the full bounceback message would also be useful.

 

If you go into the Microsoft 365 admin center and do a message trace (Security > Mail Flow > Message Trace) which will likely give you more information.

 

I've seen this before where the admin had set a transport rule that if mail gets sent to allstudents it also gets bcc'd to another address, in this case, the message was going to allstudents but they were receiving a bounceback from the secondary address.

[LeMarchand]

Have they got a forwarder setup?

 

This was the cause at my O365 school. Temporarily deactivated the block, but managed to get the users to set up their school account properly or to use the web version.

[Renfield-64]

OK thanks, I'll check this out.

[Renfield-64]

Hi, I've just done the message trace and they have got a forwarder set up which is outside of the organisation. I think this could be it.

[Katy]

Hi, I've just done the message trace and they have got a forwarder set up which is outside of the organisation. I think this could be it.

 

Microsoft changed the default behaviour recently to prevent any external forwarding.

 

See: https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/external-email-forwarding?view=o365-worldwide

 

Basically the Outbound Spam filter setting by default blocks it, you'd need to set it to allow forwarding here. You can then further control forwarding by configuring Remote Domain settings, or individual mailbox permissions, however both these are independent of the spam filter setting so the most restrictive of the two applies.

[Renfield-64]

OK great, thanks for the info.