Exchange POP Connection Error: Unknown User Name or Bad Password

We recently migrated a new acquisition over to our Exchange 2013 environment and they use Jira for customer tracking and such.
When trying to get Jira connected to Exchange, it kept throwing username and password errors over the POP3 connection.

The problem comes from the User Name and Exchange Alias not matching.

The fix is to use the full UPN: username@domain.com in the POP settings; instead of just the username.

Simple enough!