I have a following scenario:
In the domain A and Domain B. There is a userDomainA. He sends email to userDomainB that has forwarding configured on his mailbox to forward all with keeping copy to contactA with address userDomainA. Everything works fine.
Now userDomainA sends email to groupDomainB, where userDomainB is a member and getting Delivery Failed message.
There is a mail relay that allows only internal Exchange servers to send from DomainA. When sending directly to userDomainB, the email that was forwarded is received with envelope sender of userDomainB, as it should be. However, when the message is sent to DL - envelope sender is listed as userDmainA and thus being blocked by relay.
I have access to both Exchanges. Issue is reproducible with new users and groups. Any idea how I can solve it? I have a few users that has mailboxes in both domains and want the same setup