E-mail Gateway

I am in the beginning phases of developing a support system. I would like the program to be able to receiving and process e-mails. However, I am at a loss as to where to start. The main roadblock, at this point, is how to best receive and process the e-mail. I have looked at 2 options. 1) Use a cron job to execute a php script every x minutes. 2) Create a script where mail can be piped to. This is a method that I have used previously with a cgi app called PerlDesk. While I could develop the first option, the second option is the method of choice, but I have no clue how to implement that. Would anyone happen to have any suggestions on where to start? Perhaps, someplace where I could go for further research? Thank You, Jason Williard