Despamming wholesale dialup

Mon Nov 2 11:33:05 UTC 1998

> If the small ISP opens their SMTP server to the IP addresses of the big
> national dialup provider, which they would have to do in order to be able
> to handle that roaming customer who could be just about anywhere, will
> they not also be opening themselves up to being a relay for any spammer
> that uses any reseller of that national provider?  Will not such spammers
> then have access to every ISP doing reselling via that national one?

How about checking the MAIL FROM: part of the message?  If a spammer tries to
use an invalid address, the small isp's sendmail can reject it outright. 

> I think the SMTP server that should be used when dialing that national
> provider is the SMTP server provided by that national provider, unless
> some kind of VPN is used (to be more technically correct, use the SMTP
> server of the provider of IP addressing).

Yes, but how does the user know to change this?  A redirection (some policy
routing and port fudging will help,) but it may be easier for the visp client
to be authenticated in some way, (like a radius scheme that picks up the
current remote ip address of the user and allows relay from that address
while the user is online.)

TERRY