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

Matt Sergeant msergeant at messagelabs.com
Sun Jun 5 17:07:34 CDT 2011


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 :)

Jeroen Massar wrote:
> As the subject states,
>
> MAILER-DAEMON at messagelabs.com:
>
> <.... at 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 [email protected] thus no way to
> tell them through that route.
>
> Greets,
>   Jeroen
>
>
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>    

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