It can't know anything more than a yes/no on if you have mail on login. Never has been able to know more and probably never will. Bitch at Blizzard if you want it to, I'm sure they'll route your complaints to the proper trash bin ^^
LOL! No need. The green icon is perfect. I honestly don't care the number at any time. Yes/No is fine. ;D
My point though, is it seems to be working fine for me on 1.12.
Weird. It works for me. The only issue I've had is when I first login to WoW, if I have mail waiting MailFu doesn't tell me that, although the icon does change to Green. Any mail received during a session after that plays a sound, shows a notice in chat and increments the new mail number by the icon in FuBar.