Microsoft 365 — Sending from Shared Mailboxes
Microsoft Outlook using Microsoft Exchange or Microsoft 365 can support multiple mailboxes but by default will send from the user's primary mailbox.
To send a message from a shared mailbox:
- Start a new message.
- If you don't see the From line:
…choose Options → Show From.
- Click From. Enter the address you wish to send from.
If the address does not appear, click Other Email Address from the drop-down list and click From to select from the Global Address List:
This only needs to be done once. In future the shared mailbox can be selected more easily using the From button drop-down list.