Writing an Email Autoresponder Script with PHP

Fortunately, PHP fits nicely into the role of a scripting language which can talk to your application databases (to get user data), generate emails, and be called as a command-line interface by your mail program. That's the most important part-- many web languages support reading and sending emails and talking to your database, but few are accessible both as application servers and as command-line programs. I'll explain how to write such a script next.

First you need to tell your mail server to run a specific script every time an email is received for a specific account. For Qmail on Linux, you'd write what's referred to as a "dot-qmail" file. The filename should start with .qmail, then have a dash, and then the exact name of the email account that you want the script to run for. For instance, if you wanted an autoresponder for your support emails, you would create a file named .qmail-support:

| /path/to/php /path/to/autoresponder-script.php

Now for the PHP script. At the top of our script we need to initialize variables.

// Initialize variables
$from = "";
$to = "";
$cc = "";
$bcc = "";
$subject = "";
$allheaders = "";
$otherheaders = "";
$message = "";
$splittingheaders = true;

Then we add code that pulls the email in from standard input (don't worry if you don't know what standard input is; it's the way that PHP automatically gets data in command line mode).

// Get the email from stdin
$fd = fopen("php://stdin", "r");
$email = "";
while (!feof($fd)) {
    $email .= fread($fd, 1024);
}
fclose($fd);

Now copy the email into an array by splitting it by lines. This makes it easier to loop over.

// Parse the email line by line into an array 
$lines = explode("\n", $email);

Now parse the email into variables that represent individual header lines as well as the body.

// For each of the lines in the email
for ($i=0; $i

Now there you have what you really want.. all of the information in the email has been broken up into identified chunks. At this point you can run database lookups on the email address or on information in the header, or you can reply to the sender, and/or you can forward the email on. (Consult the PHP docs for more information on how to customize the mail() function.)

// Send an autoresponse back to the user
mail("$from", "Responding subject", "", "From: Responder Name ");

The rest is up to you. Of course, when creating an autoresponder like this, you always take the chance that you're going to get caught in a mail loop (where the autoresponse you send gets an autoresponse back, which gets an autoresponse, which gets an autoresponse, and so on ad infinitum). You definitely don't want this to happen-- so I use two tactics. First of all, I filter out autoresponses to the autoresponder's domain with a simple conditional statement like so:

// If the user isn't from our domain
if(!strpos($from, '@yourdomain.com'))  {
     // Then send an autoresponse back to the user
     mail(....);
}

Secondly, I keep a list of the latest 10 emails sent to the autoresponder script. If the current from address is 8 of the last 10 entries, then I suppress further responses.

// Read in the list of recent emails from the filesystem
$recentMatches = 0;
$fd = fopen("/path/to/recentList.txt", "r");
while (!feof($fd)) {
    $recentList .= fread($fd, 1024);
}
fclose($fd);

$lines = explode("\n", $recentList);
for ($i=0; $i< count($lines); $i++) {
	if($i > 0 || count($lines) < 10)
		fwrite($fd, $lines[$i] . "\n");
}
fwrite($fd, $fromEmail . "^" . $date);
fclose($fd);

// If the user isn't from our domain and hasn't sent too many recent emails
if($recentMatches < 8 && !strpos($from, '@yourdomain.com'))  {
     // Then send an autoresponse back to the user
     mail(....);
}

Oh! And don't forget to forward the original email to someone within your organization.

// If the user isn't from our domain and hasn't sent too many recent emails
if($recentMatches < 8 && !strpos($from, '@yourdomain.com')) {
	// Forward the email
	mail("First Last ", "$subject", "$message", "From: $from\n");
	mail("First Last ", "$subject", "$message", "From: $from\n");
}

Download the complete script and do whatever you like with it. It will take some customization of names, emails/domains, and system paths to work for you, but if it can save you work in the long run it's well worth your time to set up.