"George Ou" <george_ou(_at_)netzero(_dot_)com> wrote:
You're always free to implement port 25 blocking on your side for
inbound traffic which effectively achieves the same thing for your
network. You just need to implement a large ACL yourself that might
be synchronized with a large shared database somewhere on the net.
Where, precisely, is the large accurate shared database?
Every ISP knows which of its IP addresses hold machines that ought to
be allowed to send email directly outside its network. That's local
knowledge. Nobody has complete and accurate global knowledge.
Why do you want everyone else to implement outbound port 25 blocks
for you?
Because they're the ones with the accurate information.
Bottom line is, you'll have the same problem convincing people to
block outbound 25 as you will convincing them to implement SPF.
They can do both. But blocking port 25 causes their network to send
me a lot less spam, which gets them fewer complaints and makes their
legitimate email less likely to be blocked. Some networks like that.
SPF just happens to be a better solution in my opinion.
Not in the opionion of many others, some of whom are a lot more
influential.
Seth
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