email client in perl !

In my company there is a linux mail server.

I want to develop an email client which can make 3 files :
inbox,outbox and trash for each user of the system.

Their respective mails need to be stored in these files in mbox format.

Now, as soon as a user reads his mails through pop3 server, I want them

to be transfered to the 'inbox' file for that user.

What do I need to do ? How can I do this ?

Do I need to keep some particular format for that file because it will

contain emails with attachments also.

Can I tell that this is an implementation of IMAP ?

My implementation lang. is perl.