Send on Behalf

Send on Behalf is an Exchange Online permission that lets a delegated user send email with attribution to the mailbox owner — recipients see the message as "Delegate on behalf of Owner" in the From header. Distinct from Send As, which sends transparently as the owner with no attribution. Use cases: executive assistants composing meeting invites on behalf of executives where recipients should know who actually sent, or workflow service accounts sending email for a shared mailbox where attribution matters. Configured in Exchange Admin Center delegation settings or via Set-Mailbox -GrantSendOnBehalfTo PowerShell. Whether to use Send As or Send on Behalf is mostly a question of recipient expectation — invisible delegation (Send As) for shared queues, attributed delegation (on Behalf) for personal assistants.