If you want to implement SPF yourself in exim, then I believe that there are instructions off of the SPF site for exim. That said, if you have hosting customers, be sure to warn them that they will lose legitimate email if you integrate it into exim. Also be aware that SPF does nothing at all about SPAM, it's purely about preventing joe-jobbing, nothing more: http://www.openspf.org/downloads.html
Thank you chirpy
one last question
if my domain got a spf records do i need to setup exim if as a sender i want the receiver that part of of spf frame work to see my spf record ?
Because i need spf fot uotbound mailing i do not care about the inbound mailto my server