I have a client with an office365 account with a single e-mail address 'firstname.lastname@example.org'. This user does outside sales work for other companies that have their own e-mail systems and domain names, and they have created e-mail addresses for my client in their domains 'email@example.com and firstname.lastname@example.org'.
My client uses office365 OWA, Outlook and Outlook for Mobile to access email
We currently have forwarded 'email@example.com to firstname.lastname@example.org'. When my client receives an e-mail from 'email@example.com' they want to be able to reply to the e-mail and change the 'from' address to 'firstname.lastname@example.org'
How can I set this up in office 365 so they are able to change the 'from' address to the proper Domain for the reply to keep e-mail continuity?