Altering subject of email in a pop3 mailbox

Hi all. Tried to find this and can't find any info. I am writing a spam filter to run over multiple pop3 mail boxes which will work on keywords and Bayesian. With a very high score the filter will simply delete the email, with a med-high it will back the email in a 'bulk-mail' folder and delete it from the mailbox. with medium score I was wanting it to append the keyword [spam?] to the subject line and keep it in the pop3 mailbox. I can't work out how to do this in php. Can anyone help me on this one? Is it possible to alter a subject line (or body for that matter) of an email in a pop3 mailbox? Thanks. -- ------------------------ spamcatcher@selectperformers.com www.selectperformers.com