Assist me with Shared Mailbox Alias Configuration in Outlook 365

You can set up multiple aliases on a shared mailbox in Microsoft 365, but Outlook itself cannot automatically choose an alias per application — the sending app must specify the alias in the From address, and the shared mailbox must have Send As permission for each alias. In Exchange Online, aliases are added to the shared mailbox in the Microsoft 365 admin center or via PowerShell, and once they’re in place, any application or user with Send As rights can send using that alias simply by setting the From address to it. The main limitations are: Outlook desktop cannot pick an alias from a dropdown (you must manually type it the first time), aliases cannot have separate signatures or delivery rules, and some older SMTP apps may fail unless the alias is explicitly added as a proxy address on the shared mailbox. As long as each application supports specifying the From address and the shared mailbox has proper Send As permissions, using different aliases for each app works reliably in Microsoft 365.

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