@Brian--
Thanks very much, Brian, for the pointer to ADModify.Net. The development website for this very useful tool is here:
http://www.gotdotnet.com/workspaces/workspace.aspx?id=f5cbbfa9-e46b-4a7a-8ed8-3e44523f32e2
This is a good tool for every Exchange administrator to become familiar with, and it does indeed have a specific task (just mark the checkbox) to grant Send As to users who already have Full Mailbox Access (FMA). For administrators who wish to give everyone
FMA and be done with it, and don't want to mess with a script, this is a perfect tool.
One thing that the script does more easily than ADModify is show you exactly who has FMA for a mailbox. Suppose there are several users who have FMA but not Send As on Mailbox1. The script will dump you a report that looks like:
"mailbox1" "domainHasFMA-1" "Has FMA 1",....
"mailbox1" "domainHasFMA-2" "Has FMA 2",....
By deleting the 2 line and feeding the 1 line back to the script, you can grant to 1 but not 2. ADModify will force you to grant FMA to both 1 and 2--which may be just fine with you.
Keep in mind that granting "Send As" to delegates who have FMA will cause the delegate to always "Send As" instead of "On Behalf Of."