It was brought to my attention that following the steps listed in KB327000 (http://support.microsoft.com/?kbid=327000), which applies to Exchange 2000 and 2003, to assign a user "Send As" permission as another user did not appear to work. I too tried to follow the steps and found that they did not work. I know this feature works, so I went looking around for other documentation on this and found KB281208 (http://support.microsoft.com/?kbid=281208) which applies to Exchange 5.5 and 2000. Following the steps in KB281208 properly gave an user "Send As" permission as another user. But I found the steps listed in KB281208 were not complete either. The additional step that I performed was to remove all other permissions other than "Send As". Here are the modified steps for KB281208 that I performed (changes noted in blue):
1. Start Active Directory Users and Computers; click Start, point to Programs, point to Administrative Tools, and then click Active Directory Users and Computers.
2. On the View menu, make sure that Advanced Features is selected.
3. Double-click the user that you want to grant send as rights for, and then click the Security tab.
4. Click Add, click the user that you want to give send as rights to, and then check send as under allow in the Permissions area.
4.5 Remove all other permissions granted by default so only the send as permission is granted.
5. Click OK to close the dialog box.
So after I verified that the steps for KB281208 worked, I was curious as to why the steps for KB327000 did not work. What I found was that Step #7 of KB327000 applied to the permission to "User Objects" instead of "This Object Only". Here are the modified steps for KB327000 that I performed:
1. On an Exchange computer, click Start, point to Programs, point to Microsoft Exchange, and then click Active Directory Users and Computers.
2. On the View menu, click to select Advanced Features.
3. Expand Users, right-click the MailboxOwner object where you want to grant the permission, and then click Properties.
4. Click the Security tab, and then click Advanced.
5. In the Access Control Settings for MailboxOwner dialog box, click Add.
6. In the Select User, Computer, or Group dialog box, click the user account or the group that you want to grant "Send as" permissions to, and then click OK.
7. In the Permission Entry for MailboxOwner dialog box, click This Object Only in the Apply onto list.
8. In the Permissions list, locate Send As, and then click to select the Allow check box.
9. Click OK three times to close the dialog boxes.
The KB articles were updated to include correct information. But, if you had problems with this in the past, this might be why!