Here's what I do to check the number of mail messages:
mail -n -H 2> /dev/null | awk '/:.*message.*/ { print $2 }'
-- dtm- [dwm] irssi/mutt in status bar Michael Muster
- Re: [dwm] irssi/mutt in status bar Capit Nicolas
- Re: [dwm] irssi/mutt in status bar Tener Hades
- Re: [dwm] irssi/mutt in status bar Kurt H Maier
- Re: [dwm] irssi/mutt in status bar Alessandro Dotti Contra
- Re: [dwm] irssi/mutt in status bar Michael Muster
- Re: [dwm] irssi/mutt in status ba... Jeroen Schot
- Re: [dwm] irssi/mutt in stat... Michael Muster
- Re: [dwm] irssi/mutt in status bar Martin Sander
- Re: [dwm] irssi/mutt in status bar Bryan
- Re: [dwm] irssi/mutt in status bar dtm
- Re: [dwm] irssi/mutt in status bar René Wilhelm
