I don't think that's a terribly good idea, but anyway:
main.cf:
smtpd_client_restrictions = check_client_access pcre:/path/to/file
/path/to/file:
/(ppp|dialup|adsl)/ REJECT
You can move the check_client_access restriction to any other
smtpd_xxx_restrictions if you want. You probably want to implement a
stricter regexp to avoid collateral damage. Stricter expressions have
been posted here in the past. Finally, this assumes that your Postfix
has PCRE support. If not, replace `pcre' with `regexp'.
Magnus,
I can see why he would want to do that - 99% of the spam I get is
from US-based cable modem- and DSL-hosted systems. My host -
earthlink - recently reconfigured their routers to disallow outbound
email that doesn't go through their servers, and I wish all ISPs
would do that.
Thanks for telling us how to do this - I'm going to configure it and
try it out.
Wouldn't using a Dial-up and Dynamic Black List catch these, and do so
with greater accuracy since most of them delist those that were listed
in error? Add in score based analytics on the BL's and it seems you
could be more aggressive, with a lot less risk.
I personally find greylisting catches the lions share of the dialup
and dynamic ranges at this time, though I am not sure how much longer
that tactic is going to work so well.
--
Scott * If you contact me off list replace talklists@ with scott@ *
