For delivering e-mail locally I'm using fetchmail (POP3 based) + local SMTP daemon (for outgoing e-mail). I'd like to see when new e-mail arrives to my desk. It's pretty easy if you connect classic procmail with modern notification tools based on local message buses.
For GNOME command line interface to internal message is notify send. I'm adding call inside my ~/.procmailrc (after filtering out spam e-mail of course):
:0hc | grep "^From:\|^Subject:" > /tmp/mail.notify-send; DISPLAY=:0.0 notify-send "`cat /tmp/mail.notify-send`"
The result looks like this: