On using Procmail and Vacation

vacation needs a file ~/.vacation.msg, and upon running vacation -I it will create a fresh database of users in ~/.vacation.db.

It can be called from the ~/.procmailrc like this:

:0c 
| /usr/bin/vacation -a my.alias@my.com -a another.alias@mycom -a y.e.t.another@alsomine.com username
    

Of course, procmail needs to be run in order for the ~/.procmailrc to be respected. If procmail is not the default delivery agent, this can still be accomplished by setting the appropriate ~/.forward:

"|IFS=' ' && exec /usr/bin/procmail -f- || exit 75 #user"