I have created a dynamic dist grp in exchange online.
We also have a previous on prem AD with sync on.
Its a hybrid solution.
Apparently some users doesn't receive the mail i send to the DDG.
I can see the the users not receiving email was created in the on prem AD years ago.
what have i missed?
Where are their mailboxes located? Have you confirmed they are returned as actual members of the DDG? Have you run a message trace and what does it show?