Yes I was referring to a home broadband with Dynamic address.
But even for example Virginmedia's IP does not work properly and they only change the IP 1-1.5 years.
Most providers got these address blocks already, not a big deal, can be checked on ripe.net freely.
Also not to mention all SPAM filter providers, they do know these blocks already.
If you have a domain to play with, try a fix public IP address with a "wrong" not matching reverse dns address without having an SPF record for the domain. All providers Google/Hotmail/Yahoo will reject your email and will end up in the spam folder, marked as spam. Maybe I was wrong about the reject part, it will end up in the SPAM folder, clearly the user wont have it as a legitimate email.