Reading email from sendmail

Good afternoon, all!! Is there a function or series of functions in PHP that will allow a PHP package to read email from a sendmail account, look for a specific information in the subject line, then be able to resend that email to a group of users?? I know mail can be used to send email but reading from sendmail???... Any information is greatly appreciated and profoundly useful. Robin 'Sparky' Kopetzky Black Mesa Computers/Internet Service Grants, NM 87020