There are a lot of things to be checked before you can send mail from a server.
Many recipient mail servers need something called as spf record to be set at the sender's domain:
www.openspf.org/Introduction
I think , if you are not sending more than 100 mails a day , a better approach would be to use smtp mailer along with google mail
Send email using the GMail SMTP server from a PHP page
So in that way you need not mess or worry about spf or DKIM ..
Its a simple solution but your email would have something@gmail.com
that wouldn't be so professional , so if you are looking for professional solution then you need to look for setting up spf records and DKIM for your domain