Receiving Mail (POP)

The flip side to sending mail is, of course, receiving it. This is done using the POP or Post Office Protocol. Since you've already read about the SMTP protocol in detail, We'll skip describing the details of the POP.

The program pop.pl contains a program that will filter your mail. It will display a report of the authors and subject line for any mail that relates to One Word, a mailing list devoted to the great jazz guitarist John Mclaughlin (one-word@ml.ee) . This program will not delete any mail from the server, so you can experiment with confidence.

Note Before trying to run this program, make sure that the POP3Client module (POP3Client.pm) is in the Mail subdirectory of the library directory. You may need to create the Mail subdirectory. See your system administratior if you need help placing the file into the correct directory.

You might need to modify the program for other systems -- other than windows -- On SunOS 5.4+ (Solaris 2), you'll need to change the POP3Client module to use a packing format of 'S n c4 x8' instead of 'S n a4 x8'. Other changes might also be needed.

The program pop.pl operates as follows:

• Turn on the warning compiler option.
• Load the POP3Client module.
• The POP3Client module will load the Socket module automatically.
• Turn on the strict pragma.
• Declare some variables used to temporary values.
• Define the header format for the report.
• Define the detail format for the report.
• Initialize $username to a valid username for the mail server.
• Initialize $password to a valid password for the user name.
• Create a new POP3Client object.
• Iterate over the mail messages on the server. $pop->Count holds the number of messages waiting on the server to be read.
• Initialize a flag variable. When set true, the script will have a mail message relating to one-word.
• Iterate over the headers in each mail messages. The Head() method of the POP3Client module returns the header lines one at a time in the $_ variable.
• Store the author's name if looking at the From header line.
• Store the subject if looking at the Subject line.
• This is the filter test. It checks to see if the word "One-Word" is in the subject line. If so, the $one-word flag variable is set to true (or 1).
• This line is commented out; normally it would copy the text of the message into the @body array.
• This line is also commented out; it will delete the current mail message from the server. Use with caution! Once deleleted, you can't recover the messages.
• Set the flag variable, $one_word, to true.
• Write a detail line to the report if the flag variable is true.

The code for pop.pl is as follows:

#!/usr/bin/perl -w


use Mail::POP3Client;
use strict;


my($i, $from, $subject);




format main::STDOUT_TOP =
    @|||||||||||||||||||||||||||||||||||||||||||||||||  Pg @<
    "Waiting Mail Regarding One-Word",                    $%


    Sender                  Subject
    ----------------------  --------------------------------
.


format main::STDOUT =
    @<<<<<<<<<<<<<<<<<<<<<  @<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
           $from,                    $subject
.


my($username)   = 'dave';
my($password)   = 'XXXXXXXX';
my($mailServer) = 'mailhost2.cs.cf.ac.uk';


my($pop) = Mail::POP3Client->new($username, $password, $mailServer);


for ($i = 1; $i <= $pop->Count; $i++) {
    my($one_word) = 0;


    foreach ($pop->Head($i)) {
        $from = $1 if /From:\s(.+)/;


$subject = $1 if /Subject:\s(.+)/;


        if (/Subject: .*One-Word/) {
#           @body = $pop->Body($i);
#           $pop->Delete($i);
            $one_word = 1;
        }
    }


    if ($one_word) {
        write();
    }
}

This program displays:

Waiting Mail Regarding One-Word           Pg 1


    Sender                  Subject
    ----------------------  ---------------------------------
    Massimo                 [One-Word] One Word Tribute CD
    Marco                   [One-Word] Gigs in London
    Andres                  [One-Word] Pages of Fires

When you run this script, you should change $username, $password, and $mailServer and the filter test to whatever is appropriate for your system.

You could combine the filter program with the send mail program (from sendmail.pl) to create an automatic mail-response program. For example, if the subject of a message is "Info," you can automaticallly send a pmilesefined message with information about a given topic. You could also create a program to automatically forward the messages to a covering person while you are on vacation. I'm sure that with a little thought you can come up with a half-dozen ways to make your life easier by automatically handling some of your incoming mail.