Scenario: I, Alex Heer want to give user Joe Bloggs permission to send emails for me. Joe Bloggs can do this by putting Alex Heer in his Outlook's 'From' field
Send As: The email will look like its come from me, Alex Heer. The receipient should have no idea that Joe Bloggs actually sent it.
Send on Behalf: The receipient will see that that the email is from "Joe Bloggs on Behalf of Alex Heer"
To configure Send on Behalf
1) A user themselves can grant 'Send on Behalf' to another user in their Outlook Delegates by giving them Author or Editor access to their Inbox. (However bear in mind this also gives the delegate access to open their inbox)
2) Powershell: Set-Mailbox Alex Heer -GrantSendOnBehalfTo Joe Bloggs
3) Or, and probably the easiest, using the Exchange Management Console (EMC), Exchange 2010. Expand Recipient Configuration > Mailbox and open the properties of the user who we want to allow the send of behalf permission (e.g Alex Heer).
On the Mail Flow Settings tab, open the Delivery Options.
Under Send on Behalf, click Add and browse to the user we wish to grant access to (You can only assign Send on Behalf to users and not groups). Click OK
Note: Ensure that the user you are giving Send on Behalf permission to IS NOT also listed in the Send As permissions. If listed in both, Send As permission will win.
Note: If you get any errors applying changes in the EMC, this can normally point to a conflict of permissions with those set within Outlook delegates. I normally clear any permissions for that user in the delegates, then assign the Send on Behalf in the EMC, then return to Outlook delegates to reconfigure the other Outlook permissions again.
Add-ADPermission Alex Heer -ExtendedRights Send-As -user JoeBloggs
2) Using Exchange Management Console (EMC), Exchange
2010, expand Recepient Configuration > Mailbox and select the user you we want to allow the Send As permission (e.g Alex Heer).
In the right hand pane, select 'Manage Send As Permissions'. Click Add and select the user or groups you want to give Send As permission to. Click Manage