The mailbox delegation tab covers three options: Send As, Send on Behalf, and Full Access:
The mailbox delegation tab
Other members of your organization can be added to all three dialogues:
- Send As: This option allows the user who is being added as a delegate for this mailbox to send mail that looks like it comes from this mailbox.
- Send on Behalf: This option lets the delegate send mail that's marked as on behalf of from this mailbox.
- Full Access: This is actually not full access at all. The delegate can open the mailbox and can perform many of the functions that the owner can, but it doesn't include the Send ...