Need to change "return-path" on server generated mails

view story

http://www.linuxquestions.org – I have few websites running on the same server, and all these sites has some email function, When ever they send email, its return path is set to [email protected] Is there a way to change it, so that each website send a mail its return-path is set according to the site domain name? for www.abc.com mail return path is [email protected] and for www.xyz.com mail return path is [email protected] ? Thanks. (HowTos)