limitmail is a tool for sending out notification messages
via email. It works like a regular mailer, but keeps track
who it sent a message to and when. On the next call
of limitmail, it will silently discard messages to
users who already received messages in a specified
The parameter $NO_MORE_THAN_EVERY in the top section
of the script specifies this timeframe in seconds.
Bottom line: You can call this script as often as
you want, it'll send off messages to users no more
often than once in a specified time frame.