Hi,
To better assist you, we suggest to use your Outlook.com account to manage the "Alias" you want to use when sending emails. See the steps below on how to do it:
- Login in Outlook.com.
- Once done, click the gear icon at the top right.

3. Click **Options,then inConnected accounts,**hit Manage or choose a primary alias.

4. Choose how would you like to receive your code.

5. Once done, click Add email, then choose "Add an existing email address as a Microsoft account alias"


6**.**Open your Outlook application again, then try to send an email and choose the alias that you added.
Let us know how it goes.
I notice you do not show a screen clip of the alias selection within the Android app. That'll be because it still does not work.
I have 5 or 6 aliases set-up on Outlook.com, some for social use, some for serious use. You can't surely expect me to switch my default alias on the web between each email I send? Why would I use the app when I've got to use the web page so frequently?
The app is let down my this bug; Microsoft is let down by Microsoft associates not getting to understand the real problem here. The paid for Outlook app on Windows does not properly support this either...