Large mail providers such as Gmail, outlook.com
and yahoo.com
already know if an email comes from a DHCP pool and if so
they deliver such mail pieces straight to the recipient's spam
folder.
What about IPv6? Rogers and Teksavvy hand out a /56 prefix. That's
2^72 addresses that are not DHCPv6, unless you make them that.
Normally, you'd use SLAAC and I don't know if those companies would
have a list of subscriber prefixes.