Regarding consumer access, most ISPs place port 25 filters on their
access lines. A sender can only send email to a subset of email relays.
This works moderately well. Most spammers have many alternatives for
sending email (see item B) rather than via the ISPs mail server
specified within the port 25 access list.
However, if restricted by alternatives will spammers try to go through
the ISP and will that lead to the ISP cutting down on anonymity?
Being that a majority of spammers who use ISP accounts are either using
stolen accounts, or accounts they purchased with a pre-paid credit card,
I submit that even if the ISP cracks down on anonymity and is able to
identify the user on their system, the spammer will still be able to
maintain complete anonymity as a result of their utilization of the
So then we're back to square one: we've authenticated a user at an ISP
who doesn't really exist in real life =)
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