Easy  way to set-up fast, simple  and reliable email relay server which will work with ISPs smtp server.   Install EXIM4 server: apt-get install exim4  exim4-config run : dpkg-reconfigure exim4-config; choose following config:              a: mail sent by smarthost; no local mail b: you domain name (example.com) c:  loopback address d: nothing e: domain name (example.com) f: ISP’s host name – smtp.comcast.net g: No h: Yes Test,...