I think so too, but am unsure how to go abouts tracking it down. I know that a reverse dns lookup on my domain does return the corect ip, I also know that my isp uses DHCP and so my computer has a domain from DHCP and the domain I siggned up for at www.no-ip.com

I asked www.no-ip.com to store my ip which is static, for the domain I choose, then I added the domain to the access, and also my sendmail.cf, I thought that sendmail would compare the host inside my host table, to the host of the access table and then reverse dns and see I realy am who I say I am.