To see how to use other mailboxes in Webmail, see our guide How To Open Another Mailbox in Office 365 Webmail.
Note: you will need to get your IT partner or IT department to give you the correct permissions to send as or on behalf of another email address.
Show the From field
You need to first display the From field in new messages in Outlook.
Pop out a new message in Outlook to see more features in the top ribbon. Go to the Options tab and in the ‘Show Fields’ group choose ‘From’
Next, you should select the email from the address book, rather than typing it manually, especially if the email has only recently been created.
Under From, choose ‘Other Email Address’
Then, click From
Change to the Global Address List (the default selection is the Offline Global Address List, but this only updates every 24 hours or so, so might not contain recently added addresses).
Select the email address you want to send from, and click though to get back to the message.
You will now be able to select the email in the From Field
A couple of points to note
If you are writing a new message, even if you are in the Inbox of another mailbox, the new message will always by default be sent from your main account, so you will need to choose the other email address for all new messages
If you are replying to an email in a shared mailbox, the email will by default send from that shared mailbox’s email address.
Emails sent from another address will always appear in your own Sent Items, not the Sent Items of the shared mailbox. If you need other colleagues to see the messages you have sent, you will need to move them into the shared mailbox.
