We are using MS 365 Exchange email synchronisation with Odoo. The forwarding rule is based on the recipient not being a member of a dynamic user group.

Some people in my domain and guests in my tenant get this strange bounceback email when sending things to me. I am in the dynamic group - I own it - and the email address appears to be correct. 

The message below could not be accepted by the address bla@blahblah.com. Only addresses linked to registered partners are allowed to contact it.

Has anyone else encountered this?