I have server which is hosting few websites. When user fills form on a website I get it from root@webserver instead from mail which belongs to the hosted website. How can I check why is this happening?
Webserver is running RedHat 5 linux.
You need to configure the mail server (which is the software actually doing the delivery) to re-write the mail headers for you. The default mail program for Red Hat 5 is Sendmail but you can easily use Postfix instead (I find postfix easier to configure especially if you are new to mail servers).
To change the name after the @ you need to use the masquerading configuration options. See the documentation for how to do this (or do some Google-ing) but I recommend reading up on how mail servers work a little first.