Post Migration, you may find your emails missing from your Android or iOS devices from Outlook App.
It happens because, your phone's Outlook still thinks that you emails are pointing to the old server and not Microsoft.
In order to fix this issue, all you need to do is delete your email account from the Outlook app and re-add it.
To remove the account, go to Outlook Settings, and you will see your account under Email Accounts.
Click on the account you want to remove, scroll down to the bottom of the screen and click 'Delete Account'
Once it is deleted, you can move to re-adding it.
When you will re-add the account, it may ask you for your email provider.
Select 'Office 365'
Post that, it will take you to Microsoft sign in screen, to enter your new password.
Enter your password
You will now be signed in to Outlook. Once done, you will see that all the emails are up-to date.