The DNS approach will tend to be somewhere between free and cheap for
mainstream uses.
I keep seeing this assertion, but it makes no sense. As a concrete
example, here's the DNS for the POP server for BT Internet, the largest
ISP in the UK. Can you describe the DNS changes needed if they were
publishing a spam button address?
R's,
John
$ dig mail.btinternet.com a
;; ANSWER SECTION:
mail.btinternet.com. 600 IN CNAME pop-smtp.bt.mail.yahoo.com.
pop-smtp.bt.mail.yahoo.com. 1800 IN CNAME
pop-smtp.bt.mail.fy5.b.yahoo.com.
pop-smtp.bt.mail.fy5.b.yahoo.com. 300 IN A 217.12.13.134
pop-smtp.bt.mail.fy5.b.yahoo.com. 300 IN A 217.146.188.192
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