When we try to send a message on belief of another user, we can select the From user from the GAL and it works fine and the from user in the emil says its from that user.
If we select the from user from the MRU list (the same user that just did work), that message will come back as undeliverable with the Error:
Scott Townsend (the person I was sending to)
You can't send a message on behalf of this user unless you have permission to do so. Please make sure you're sending on behalf of the correct sender, or request the necessary permission. If the problem continues, please contact your helpdesk.
Diagnostic information for administrators:
Generating server:
/O=EMAILORG/OU=MAILSERVER/cn=Recipients/cn=S_Townsend
#MSEXCH:MSExchangeIS:/DC=com/DC=AD-DOMAIN:SERVER-EXCHANGE[578:0x000004DC:0x0000001D] #EX#
Exchange Server : Exchange 2010
Client: Outlook 2016
Thank you,
Scott<-