Hello,
It's dovecot which you need to configure to achieve the desired. Check these pages from dovecot mailing lists:
http://www.dovecot.org/list/dovecot/2011-December/062659.html
http://www.dovecot.org/list/dovecot/2010-March/047820.html
http://www.dovecot.org/list/dovecot/2008-March/029181.html
To say it short, yes it is possible, either by modifying permissions on emails at system level, or by configuring ACLs in dovecot.
protocol pop3 {
mail_plugins = acl pop3_acl
}