Bummer...

By "inactive" I mean if it never gets to an inbox because that email account no longer exists at that organization.

Sadly (I guess), it doesn't sound like this is something that's possible. However, when I was tinkering (which is about all I can really do with Perl) I came up with a script that checks for invalid / valid email accounts by trying to send a dummy email. Although I'm not sure if it's doing what I hope it's doing.

In the code below I have three email addresses from our organization domain name. The first in the array is a valid email (mine). The second and third are invalid. Seems to pull out the invalid ones like it should, and no actual email gets sent *shrugs*. Can anyone tell me what this is really doing?

#!/usr/local/bin/perl
use CGI qw(:all);
use Net::SMTP;
# Checks email to see if it's active

print header;

gatheremails();
results();

## GATHERS EMAILS
sub gatheremails {
# The first element of the array is my valid email, the others are dum
+mies.

    @emails = ('jhess@wilcoxassoc.com','jhess1@wilcoxassoc.com','jhess
+2@wilcoxassoc.com');

    foreach $email(@emails){
        checkit();
    }

}

## CHECK THE EMAIL BY DOING A MAILSEND
## WITHOUT REALLY SENDING ANYTHING
sub checkit{
## SMTP BEGIN
    $smtp = Net::SMTP->new('mail.wilcoxassoc.com'); # connect to an SM
+TP server
    $smtp->mail('webmaster@wilcoxassoc.com');     # use the sender's a
+ddress here
    $smtp->to($email) || addinvalid($email);       # recipient's addre
+ss
    # $smtp->data(); # Start the mail


    $smtp->quit;
    # Close the SMTP connection

    # If the flag shows it's not a bad email
    # then put in $email into the @valid array.
    if ($emailisbad ne "1"){
        # GROWS AN ARRAY OF VALID EMAILS
        push(@valid,$email);
    }
    # Reset the flag to 0 for next email
    $emailisbad = "0";
}

# PRINTS THE RESULTS TO THE BROWSER
sub results{
    print "<center><h2>Check for Active Emails</h2></center>";
    print "<p>Active Email Addresses:";
    print "<br>----------------------<br>";
    if (@valid){
        foreach $valid(@valid){
            print "<li>$valid</li>";
        }
    }
    print "<p>Inactive Email Addresses:";
    print "<br>----------------------<br>";
    if (@invalid){
        foreach $invalid(@invalid){
            print "<li>$invalid</li>";
        }
    }
}

# GROWS AN ARRAY OF EMAILS THAT ARE INVALID
sub addinvalid{
    my ($errmsg) = @_;
    push(@invalid,$email);
    $emailisbad = "1";
}
[download]

That will work for some mail servers. Others will accept all mail, and later generate a bounce for it. qmail behaves this way, for example. If you tried using this, VRFY, EXPN, and also checking that the domain still exists, you might be able to trim some users from your list, but not all. It's probably easier to just send the mail and watch for bounces.

For bounces, BTW, you should consider using something like VERPs. The general idea is you set up a catchall mailbox for bouncetest-*, then send out each message with a unique sender that starts with bouncetest-. qmail's VERP implementation encodes the recipient email address into the bounce address, although you can put anything you want there. Then when you get a bounce, you know what message you sent caused it. It can be surprisingly hard to figure this out otherwise, either programatically or by hand.