We have a single Exchange Server running Exchange 2007. We have a user that was formerly able to send on behalf of a special emailbox that receives public inquiries. The user is using Microsoft Outlook 2007 on a Windows XP workstation with the latest service pack and patches. Suddenly, two weeks ago, he is unable to send as the user and gets a notification stating "You do not have the permission to send the message on behalf of the specified user." We have tried the following: Ensuring that he was in the right security group (as it's a security group that is applied to handle permissions).Checked that he has "Send as" permission on the mailbox in questionWe even added the mailbox as Send As permission for him. Had him try logging in on another computerCleared his profile on his local computerChecked with other users that have the exact same settings, permissions and OU as he has and could find no problems with them sending emails from said email address. The ONLY thing that has changed in the last week is that we went through and removed several email boxes from showing in the GAL... one of which was this email box, but we have since readded it to the GAL (in troubleshooting his problem). Anyone have any ideas? Thank you kindly, Jason GFMS Support

Try Removing the Permission over that Mailboxes and Readd it. SID change ..Might not be updated on the Target mailbox. Satheshwaran Manoharan | Exchange 2003/2007/2010 | Blog:http://www.careexchange.in | Please mark it as an answer if it really helps you

We tried removing the permissions and re-applying them which did not work. Haven't tried a SID change though. Is there a utility for that? Should we do the SID change on the user or on the mailbox that they are trying to send as?Jason

Satheshwaran, Thank you for getting back to me so promptly. Yes, I did remove and re-add the user to the security group as well. I did check inherited permissions as well and they are identical to the users (inherit allowed) that have it working. Any other thoughts? Regards, Jason Jason