These features seem to stump the Microsoft support staff, so I'm loosing hope. The Android Outlook app is ignoring my default alias email address I have selected in Settings, Accounts, Advanced Settings, Set Default email address. This is also set in Outlook.com's permanent settings, and working perfectly using the web app for Outlook.com. Under 'Settings' in the app, 'Default' lists only the primary Microsoft hotmail.com account, Not my preferred/Default email account. There is not a 'Reply-to' custom field I could find either. A Microsoft Answer Tech recommended I create/verify that I had an Alias created for my desired email From/Reply address. So after creating this alias, and setting it as Primary alias, as I was instructed, the Android Outlook app still does not recognize it as my primary alias and displays the unwanted email address.