Sending Email from Alternate Email Aliases in Office365

You are only able to send email from your primary email address.  If you need to send email from one of your other email aliases, you will need to login to passport and change the primary email address listed there.  Then you will need to wait some time to make sure the address has updated in the necessary systems.

Please note that when you change your primary email address, you may also end up having problems with your mailing lists, so you will likely want to change back to the primary address you had set initially.