messagelabs.com contact - SMTP-side domaincheck checks IPv4 only, rejects domains with first MX on IPv6

[Jeroen Massar <jeroen () unfix org>]

As the subject states,

MAILER-DAEMON () messagelabs com:

<....@ford.com>:
Connected to 136.1.7.8 but sender was rejected.
Remote host said: 501 Sender domain must exist

As it obviously checks only the first MX record if there are A records,
and if there are none it rejects it. This while there are AAAA records
on the first MX, and even A records on the remaining MXs. Thus a proper
fix would already be to check the other MXs and of course to check for
AAAA too ;)

And that affects all customers at messagelabs, thus if somebody can pass
that along to them to fix it, that would be great ;)

Oh and of course the check is also there for postmaster@ thus no way to
tell them through that route.

Greets,
 Jeroen