We use ADMT to migrate domain from A to B, and also move some of the ex2016 mailbox in domain A to ex2019 in domain B. Some mailboxes in domain A configured auto forward to a domain A distribution group, the group set to delivery by “only sender inside my organization”
We found when domain B user send to these domain A mailboxes, they will receive a NDR from domain A Exchange said “Remote Server returned '550 5.7.1 RESOLVER.RST.AuthRequired; authentication required“.
Tested if they send to the group directly, the email can send out normally.
How can we solve the NDR problem so domain B user can send email to these mailbox and also forward to group?