We actually *insist* that our dialup providers either block port
25 or let us do the DNS/radius filterting so we can do it ourselves.
Like was mentioned below, *we* didn't want people creating
account after account and abusing other services. We trust
our antispam methods more than we trust the endless supply
of open relays out there.
--
Michael Boyiazis
[EMAIL PROTECTED]
Mail Architect, NetZero, Inc.
> -----Original Message-----
> From: -dsr- [mailto:[EMAIL PROTECTED]]
> Sent: Sunday, November 19, 2000 8:01 PM
> To: Amitai Schlair
> Cc: [EMAIL PROTECTED]
> Subject: Re: SMTP on a port other than 25
>
>
> On Sun, Nov 19, 2000 at 10:36:50PM -0500, Amitai Schlair wrote:
> > on 11/19/00 4:23 PM, Phil Barnett at [EMAIL PROTECTED] wrote:
> >
> > > Several of my pop before smtp users have found that their
> providers
> > > are blocking outbound traffic destined for port 25.
> >
> > I'm having the same problem, so far with EarthLink. Have
> you encountered any
> > other ISPs that do this? If there isn't already a list
> somewhere, please
> > send your villains to me, and I'll compile and post the results.
>
> They aren't really villains, per se.
>
> Imagine that you are an ISP. You've grown large enough to
> want to expand
> outside your original area of operations; you aren't rich
> enough to place
> physical dialup POPs all over the country/continent/world.
> What do you do?
>
> You contract with one of the big players to provide modem service for
> your customers. AT&T, UUnet, Genuity all sell dialup service
> in bulk to
> smaller ISPs - who then provide the customer service, the servers, the
> tech support and marketing and so on.
>
> In fact, this is reasonably cost-effective for large ISPs
> too: AOL does
> it, NetZero does it. And what do we know about where spam
> comes from? Spam
> comes from sources where there is no trust between the ISP
> and the customer,
> so that the miscreant can create a thousand throw-away
> accounts and lose
> them at will. abuse@whereever takes a beating. Pretty soon, ISPs close
> down relaying for anyone who is not a customer. Shortly
> thereafter, spammers
> start sending SMTP directly from dial-up smarthosts.
>
> Now the ISP is off the hook: the spam no longer contains any
> particular
> links to them. (Well, it doesn't have to, anyway.) But the
> giant dialup
> provider has supplied the IP address for the spammer, and
> pretty soon the
> calls start rolling in to abuse@dialup.
>
> To prevent this, the dialup providers now put in a new
> element to their
> contracts with the local ISPs: port 25 will be restricted on
> each connection
> to only talk to the local ISP's mailserver and backup MX.
>
> ...and that's where we are in the cycle now. The onus for
> removing spammers
> is back in the hands of the ISPs who sign them up as
> customers, but as a
> result, honest folk get restrictions on what they can do with
> their mail.
>
> -dsr-
>
