3.10 SMTP RSET and Milter Abort Handling

In previous section we have used a global variable to hold certain information and share it between handlers. In the majority of cases, such information is session specific, and becomes invalid if the remote party issues the SMTP RSET command. Therefore, mailfromd clears all global variables when it receives a Milter ‘abort’ request, which is normally generated by this command.

However, you may need some variables that retain their values even across SMTP session resets. In mailfromd terminology such variables are called precious. Precious variables are declared by prefixing their declaration with the keyword precious. Consider, for example, this snippet of code:

precious number rcpt_counter

prog envrcpt
do
  set rcpt_counter rcpt_counter + 1
done

Here, the variable ‘rcpt_counter’ is declared as precious and its value is incremented each time the ‘envrcpt’ handler is called. This way, ‘rcpt_counter’ will keep the total number of SMTP RCPT commands issued during the session, no matter how many times it was restarted using the RSET command.