The username field is treated as a mandatory field in the outgoing mail server configuration when using Oauth 2.0

Issue Summary

The Oauth 2.0 authentication for the Outgoing Mail Server functionality was introduced in Jira 9.2.0 as per Jira 9.2 release notes.

In the ⚙ > System > Outgoing Mail configuration page, the following is mentioned:

Optional - if you use authenticated SMTP to send email, enter your username.

However, when configuring an Outgoing Mail Server and when testing the connection, we are forced to enter something in that field, even though this behavior does not make sense when using the Oauth 2.0 authentication, the Oauth authentication does not need a username: instead, the Jira application should use a token obtained earlier during the authorization process (and after logging into the MS portal) to authenticate against that mail server and test the connection.

Therefore, there are 2 problems here:

• this field is mandatory while it should be optional (especially when using the Oauth 2.0 authentication)
  
• if this field is not correctly filled in (the browser might automatically autofill this field with a random user), we might run into the following error:

  Unfortunately no connection was possible. Review the errors below and rectify:
  AuthenticationFailedException: 535 5.7.3 Authentication unsuccessful [XXXXXXXXXX.XXXXXX.PROD.OUTLOOK.COM]
  

  

Steps to replicate

• Install Jira 9.2.0
• Configure an Oauth 2.0 integration in ⚙ > Applications > Application links
• Configure an Outgoing Mail Server in ⚙ > System > Outgoing Mail, and select the Oauth integration as the authentication method
  • Leave the username field empty
• Authorize the mailbox
• Test the connection

Actual Results

The connection test is not executed when the username field is not filled in, and the Jira admin user is forced to enter a username.

Expected Results

The connection test should be executed even if the username field is not filled in