This is how to send emails on behalf of a shared mailbox (e.g. office@company.com). Requirement: send permission for the mailbox has been set up.
Outlook (classic)
Click New Email.
In the ribbon, turn on Options › From (only needed the first time).
Above the recipient field, click From › Other Email Address ….
Enter the address of the shared mailbox and confirm with OK.
Write and send the email as usual.
New Outlook and Outlook on the web
Click New mail.
In the ribbon, choose Options › Show From (only needed the first time).
Click From. If the address is not listed, choose Other email address and enter the address of the shared mailbox.
Write and send the email as usual.
Outlook for Mac
Click New Email.
Select the shared mailbox in the From field.
Tip: The address only needs to be entered once. After that, it can be selected directly under From. On Mac, the mailbox must be added first, see “Add a shared mailbox – Outlook”.
Note: New permissions can take up to 60 minutes. Sent emails are stored in your own “Sent Items” folder by default. Support can change this on request.