There is one further piece of automation possible. Once the PPP link is
established, pppd looks for /etc/ppp/ip-up. If this script
exists and is executable, the PPP daemon executes the script. This
allows you to automate any special routing commands that may be
necessary and any other actions that you want to occur every time the
PPP link is activated.
For example, you can get sendmail to dispatch any waiting outbound messages in the mail queue.
Similarly, you can insert the commands into ip-up to collect (using pop) any email waiting for you at your ISP.