I'm using courier POP3/IMAP (Maildir is ticked). I was able to login to UebiMiau now by using the email address instead of the actual username. i.e. in the username field I entered firstname.lastname@example.org
and then the same password, Voila I'm in. Now there's an odd behavior though, when I'm sending emails to my exchange server (i.e. my email account), the first email I sent went through instantly. After that I quickly followed it with another email, It never went through. I tried restarting the postfix service and then did another test. First email went through but the succeeding emails didn't.