Administrative assistant sends meeting requests to another exchange environment (yes crosses Internet) using send on behalf of the administrator and when received the meeting request email has no response buttons and appears to just be a regular email. That same assistant sends a meeting request from her own account to the same person and the meeting request appears normal with response buttons. Does the send on behalf have a different format that a mail spam (Proofpoint is being used) product may be altering the "send on behalf" meeting request but not a standard email request? Thank you in advance.

Hi Send on behalf email always is blocked by firewall. Send on behalf is just permission. You also give Send As permissions by clicking the Permissions tab. The difference is that when you give Send on Behalf Of rights, when an internal recipient receives the message, the From box is displayed as "user1 on behalf of user2". If you give Send As permissions, this text is not displayed. You can read this KB. http://support.microsoft.com/?kbid=266145 Please post your exchange and outlook version. Do you receive meeting request By Blackbarry ? I can find similar thread about 2007. You can read this thread. Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.