Great Circle Associates List-Managers
(June 2002)

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Subject: Re: connecting to [WAS: Re: ...I
From: Nick Simicich <njs @ scifi . squawk . com>
Date: Sun, 30 Jun 2002 02:08:38 -0400
To: List-Managers @ greatcircle . com
In-reply-to: <20020629160250 . A1041 @ clifford . inch . com>
References: <5 . 1 . 0 . 14 . 2 . 20020629033852 . 03cd4eb0 @ 127 . 0 . 0 . 1> <Pine . GSO . 4 . 43 . 0206281707270 . 10202-100000 @ saltmine . radix . ne <5 . 1 . 0 . 14 . 2 . 20020629033852 . 03cd4eb0 @ 127 . 0 . 0 . 1>

At 04:02 PM 2002-06-29 -0400, Omar Thameen wrote:
On Sat, Jun 29, 2002 at 03:51:22AM -0400, Nick Simicich wrote:
> Topica is in the process of being added to a number of blocklists, and I am
> unsure if this is the issue at Verizon. (At least, this is the way I
> interpret the discussion on SPAM-L).  If there was a bounce available,

Is that SPAM-L @
COM , or something else?  I've been
looking for another mailing list pertinent to list hosting providers,
particularly those hosting large lists.  Any recommendations?

Yes. I think it is pertinent because of the same reason that this list is pertinent. You hear things regarding how e-mail is handled and what people expect in terms of "best practices".

> seeing it might help.  Feel free to e-mail it to me privately.

There's no bounce, it's just a "connection refused" from (their MXer).

Odd. That sounds like they have the servers blocked at the border routers or they have done something else specifically to filter them. is a single IP address. It is priority zero MX from and they only have the one IP address. However, if you try connecting to port 25 on the system repeatedly, you get different banners. This means that they are likely using some sort of "dispatching" system of the sort used by IBM from the Atlanta Olympics on, that routes the initial connection packets (and the rest of the packet in that connection) using stateful routing. (Or they could be using a circuit level proxy that simply punches a tcp forwarding connection to one of several servers, but that is the "low tech" method - the other method only requires that you track syns and fins and origin/destination tuples -- and you only have to handle the packets that are headed to the servers, the return packets can be routed.)

I have no trouble telnetting to port 25 on those servers. There may well be some sort of issue with some server/firewall combinations that do not work well with connection dispatchers (although they are supposed to be completely transparent). All they do is (typically) change the mac address on the far end to vector your syn to one or the other of the back end servers --- and then they have to remember state so that they can forward any of your other packets that are part of the same connection to the same server.

I can imagine some sort of incompatibility with a load balancing connection router, but a circuit level one probably can't be incompatible with anything.

Even if there is a icmp filtering issue, this should not cause connection refused.

> However, there may well be some escalation blacklisting regarding
> topica.  They have had some large number of lists with spamtrap addresses
> signed up onto their service and they have not vetted them well. They also > have some subsidiary who is more, shall we say, oriented to delivering less
> solicited mail, and that subsidiary delivers from the same servers.

Hmmmm.  Is their subsidiary that (or something like
that)?  I'm just curious.

I think so. I can't remember exactly - it is not my attempt to be evasive, I just do not remember.

> So, if I was looking for uninterrupted service and my mailing list was
> actually opt-in, I would go
> elsewhere for mailing list service.

The issue I emailed about is not a list I have at Topica.  It's with
some of our servers.

Well, I was confused.  Not the first time.

War is an ugly thing, but it is not the ugliest of things. The decayed and degraded state of moral and patriotic feeling which thinks that nothing is worth war is much worse. A man who has nothing for which he is willing to fight, nothing he cares about more than his own personal safety, is a miserable creature who has no chance of being free, unless made so by the exertions of better men than himself. -- John Stuart Mill
Nick Simicich - njs @
scifi .
squawk .

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From: Vivek Khera <khera @ kcilink . com>
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