Currently there are no MX records pointing to my server. Will I need to change any MX records to get php sendmail working? I only need php to be able to send mail (on multiple virtual domains...). Also do you recommend sendmail or postfix? thanks...
Postfix is much easier to configure, so I say Postfix any day.
You won't have to change any MX records just to send mail. Just configure Postfix properly and you're good to go.