This has been discussed many times, but I still haven't found a solution for our case. Affected users so far have been administrative, which makes me think it's something to do with the Protected Group issue where it removes every hour, the ability to send email. However these admins sent email just fine in the old domain, so I'm still not sure how that applies. I tried running the PS command to add the external domain\user with SendAs rights. For some reason, I can't see this in the EMC, but the EMS says it's there. ???? Added NT Authority/SELF as well under the EMC Full Access and Send As - no luck. To clarify, it's is the "Unable to send on BEHALF" message that we're getting, not the "Send As" - so maybe this is where I'm going wrong with the above commands. Also to clarify - the Exchange 2007 server still resides in the old domain, there is a full trust between them. Thank you for any suggestions!

Hi, As you noted Send As and Send on Behalf are two different permissions. Can you run: - Set-Mailbox UsersMailbox -GrantSendOnBehalfTo UserWhoSendsonBehalf Also send of behalf won't work if the mailboxes are hidden from any address lists. Sean Massey | Consultant, iUNITE Feel free to contact me through My Blog, Twitter or Hire Me. Please click the Mark as Answer or Vote As Helpful button if a post solves your problem or is helpful!

hi, Could you explain your topology and your issue in more detail? Per my understanding, it is: Two forest: one is windows2003 and the new is windows2008/Trust between them. You only have one exchange 2007 and still reside in windows 2003 forest. You migrate your user account to the new forest.(so now your exchange topology is exchange resourse forest, you are now using linked mailbox) Then you grant send on behalf permission to migrated user and it doesn't work. If i am wrong, please feel free to correct me. thanks, CastinLu TechNet Community Support Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com

CastinLu, That is all correct. The thing I think I may have missed is the granting of "Send On Behalf". I granted "Send As". Sean - I haven't run that command. On the UserWhoSendsOnBehalf - can I specify the new domain along with the user name? Set-Mailbox UsersMailbox -GrantSendOnBehalfTo UserWhoSendsonBehalf Thanks for your responses.

Castinlu, One clarification on your original post - everything you said is correct, that is our model. However what is the definnition of a "linked mailbox" - I didn't do anything to the mailboxes to link them to the domain. I have test users who moved over without incident and work fine without any meddling. However, other users who are getting the error message about not being able to send "on behalf of" the logged in user, when attempting to send an email from their Outlook client. thnx