Secondary "from" address are unavailable sending email

Q: How can I set the from address to match a shared mailbox when send a message?

A: Using the web MS365 client setting an alternate from address is is done on the ribbon with the send button.  For some mailboxes it is unavailable until turned on.

If this area is blank you can enable the setting using the following instructions:

1. Click on the Settings (the gear icon) on the upper right of the screen next to your name
   
2. Under Settings (the gear icon) select Compose and reply 
3. Check the Always show From box.
   
4. To select an alternate from email click on the down arrow to the right of the send button
5. If you have never sent from that email before you will have to type in the email address that you want to send from