nanog mailing list archives
Re: messagelabs.com contact - SMTP-side domaincheck checks IPv4 only, rejects domains with first MX on IPv6
From: Jeroen Massar <jeroen () unfix org>
Date: Mon, 06 Jun 2011 10:20:09 +0200
On 2011-Jun-06 00:07, Matt Sergeant wrote:
I'll get someone to contact Ford and see what they are running. From google it looks like Exchange. Is this a known bug with Exchange? If so I think there's bigger problems than messagelabs :)
Ah good catch, indeed the messagelabs.com SMTP is not the blame here, it forwards it internally to a ford.com one which rejects it. One of the mail servers that is broken in that respect upto a very recent version is Communigate Pro. As for the backscatter that the above setup can generate, you might want to implement the same checks on the front-ends, or at least ask the customers you are forwarding to to disable these checks at least for your frontend servers as now as you can see, the messagelabs.com smtp accepted the email and then started rejecting it. If somebody thus nicely 'forges' (well just fills in a random) email address, the ford.com server will reject it, and messagelabs starts spamming them with the full message which is included in the bounce.... Oh, gee, now lets hope spammers don't abuse that 'feature' eh... Greets, Jeroen
Current thread:
- messagelabs.com contact - SMTP-side domaincheck checks IPv4 only, rejects domains with first MX on IPv6 Jeroen Massar (Jun 05)
- Re: messagelabs.com contact - SMTP-side domaincheck checks IPv4 only, rejects domains with first MX on IPv6 Matt Sergeant (Jun 05)
- Re: messagelabs.com contact - SMTP-side domaincheck checks IPv4 only, rejects domains with first MX on IPv6 Jeroen Massar (Jun 06)
- Re: messagelabs.com contact - SMTP-side domaincheck checks IPv4 only, rejects domains with first MX on IPv6 Matt Sergeant (Jun 05)