Email

Outlook

Exchange

Setting up Reverse DNS Lookup

http://www.amset.info/exchange/dnsconfig.asp

Reverse DNS lookup

www.relays.osirusoft.com/cgi-bin/rdns.cgi

http://postmaster.aol.com/cgi-bin/dns_tool.pl

Advanced Reading

Email Best Practise

http://www.linuxmagic.com/best_practices/check_dynamic_reverse_dns.html