zmail is a simple set of 2 functions and associated environment variables to
perform mail notification at the command line with zsh.

There are 2 basic requirements to use zmail:
    1. zsh (duh)
    2. You must use the maildir format to store your mail. This usually consists
       of each mailbox having a directory, with subdirectories new, tmp and cur
       under it.

If you meet these, move on.

To actually use zmail, you must perform 2 steps:
    1. Source zmail.zsh, manually if you want to test it, put it in zshrc if you
       want it permanently.
    2. Set up the precmd and/or the periodic function to check for mail, or do
       it some other way (cron comes to mind).

The first is obvious, so I'll focus on the second one.

The zmail_count() function is meant to go through your mail directory and count
your new mail. For large mail hierarchies, this can be slightly expensive,
though I have not noticed any severe performance hits. This mail counting can be
done in one of several places, depending on how often you want to count it.

precmd is a zsh special function which is executed before each prompt display.
periodic is another special function, which is executed at regular intervals.
zmail_count can be invoked inside either of these functions (and set the PERIOD
accordingly), to give you a pretty up-to-date mail count. Of course if you use a
cron-based mail fetch to get mail from a remote server, the best place to call
zmail_count would be right after the cron task. You can also use a program like
incron to watch the home maildir (I'm working on how to set this up, indeed it's
an application mentioned in the description of the incron package in debian).

Regarding the display, since it's a cheap function you can easily put it in
precmd and forget about it. However if you wish to avoid a mailman report each
time a new prompt is rendered, you'll need to detect changes with something like
this:

    zmail_count
    (( $MAILTOTAL > $LAST_MAILTOTAL )) && zmail_display
    LAST_MAILTOTAL=$MAILTOTAL

This will invoke zmail_display iff the total mail has increased since the last
time it was displayed.

zmail was written by P.C. Shyamshankar <sykora@lucentbeing.com>, and is
currently being hosted at http://github.com/sykora/zmail/.

Any suggestions on bugs or improvements are appreciated.