Please don't put "sent from mobile Outlook" as my default email signature every time I reinstall. Not professional.
It appears unprofessional and of the least value for me.

Hey there!
Thank you all for your patience, it is possible to set a signature for each of your email accounts in the Outlook app.
To do so open the app and go to Settings> Scroll down and tap on the Signature option> Tap on the Per Account Signature toggle on the top right of the screen.
You will now see each of your email accounts listed along with their current signature, Tap on each signature to customize as needed.
If you have any trouble with this feature please contact our in app support team by going to Settings > Help & Feedback > Contact Support.
All the best
The Outlook Mobile Team
PS: Please use the Help Section of the app for any questions, we are not able to see replies to this address.