How do I receive email and process it in a web application

I recently worked on a project that required parsing of email from gmail and updating database with certain values based on the contents of the email. I used the ezcMail (now) Zeta Components library to connect to the mail server and parse the emails.

The strategy I adopted was to filter all interesting incoming mail with a label "unprocessed". Run the PHP script via a crontab every 15 minutes. The script would connect to the mail server and open the IMAP unprocessed folder and parse each email. After inserting the interesting values into the database, the script moves the files to another IMAP folder "Proccessed".

I also found IMAP to be better than POP for this sort of processing.

Use procmail if it is installed on your system. Put these lines in a .procmailrc file in the home directory of the user who receives the e-mail.

:0
| /path/to/your/script.php

Or you can also use a .forward file containing

"|/path/to/your/script.php"

Procmail has the advantage that it allows you to deal with more complicated filtering if your application ever requires it.

Your script.php file will read the headers and body of the e-mail from stdin.

I suggest using Zend_Mail component of Zend Framework.

You need to implement an email client in Php. This is probably going to be a POP client.

This code would query the POP server containing your email, download it, and then you could parse it as needed.

A quick google search of "POP client php" has revealed a vast array of different options. Its hard to tell if there's really "The One True PHP POP Library", otherwise I'd include it here. If you are using a preexisting framework, you may wish to check to see its level of POP support, otherwise check the google results above and take your pick. Or it may just be easiest (and most educational :) ) to roll your own.

There is a great tutorial for this here:

http://www.evolt.org/incoming_mail_and_php

which covers how to have the emails forwarded directly to your script, which your script reads via stdin (fopen, fread, etc.) The tutorial code even does basic parsing of the header/body for you.

If you want to avoid reaching out over POP or IMAP to another server to pull-down the email, you can add a 'hook' into the email receive process on some SMTP server you set up (possibly the same php server). Then just have the destination email handled by this server.

Here is an example with postfix, but similar things are possible with sendmail as well.
http://www.adkap.com/autoresponder.html