On 5/10/05, John C Klensin <john+smtp(_at_)jck(_dot_)com> wrote:
Unless you abandon mail relaying, and perhaps even if you do,
domain names and IP addresses are as easily spoofed as full
email addresses. The spammers figured both out many years ago.
you're mistaken. udp spoofing is easy BUT smtp uses tcp.
its almost impossible to spoof tcp sessions now.
spoofer needs to correctly guess the randomly generated sequence/ack
numbers. even if you magically do this, you gotta control ALL
intermediate routers or else smtp server's responses will be misdirected.
meaning you cannot create a normal tcp session.
it's a common misconception that "ip spoofing"
can be used to hide your ip address while surfing the net,
chatting on-line, sending e-mail, and so forth.
this is not true unless you're on the same subnet as victim
where you can sniff their tcp seq. #'s.
if whay you say is true, all DNSBLs would stop working dude.