Re: Multiple Mail serves under one domain

[Charles Cazabon <qmail@xxxxxxxxxxxxxxxxxxxx>]

Philip Tong <philt@xxxxxxxxxxxxxxxx> wrote:
> 
> > > I'm encountering problems where certain SMTP servers (receipients's
> > > domain) are not answering Server B's connections. I have tried
> > > telnetting to the receipient's SMTP server on port 25, it will just time
> > > out. If I do the telnet on Server A, it will work.
> > 
> > Okay.
> > 
> > > Is it that these SMTP servers are configured to check against the MX
> > > records of my domain to verify authenticity of my SMTP servers?
> > 
> > No.  It could be because of connectivity problems somewhere between your
> > ISP and the remote system, or because of blacklist issues.  The qmail-send
> > logs on "server B" show that qmail successfully looks up the MX records in
> > question, but that it fails to connect?
> 
> The thing is that Server A and Server B is on the same subnet going out the
> same router. For message that the receipient refuses to establish connection
> I will get the following event in my log with the error message
> 
> Sorry,_I_wasn't_able_to_establish_an_SMTP_connection._(#4.4.1)

Okay.

> The thing is since both servers are on the same subnet, how come, Server A
> gets through without any problems but Server B will be left to just timeout?

You'll hate this answer, but it's the only one possible: because there is a
difference between "server A" and "server B", and since you're the only person
who can possibly know the differences between them, we can't help you.

It could be as simple as having TCP ECN disabled on A and enabled on B, and
the site you're trying to send mail to being behind a router/firewall which is
ECN-retarded.  It could be more complex, such as the site accepting packets
from A's address, but dropping packets from B's address for
administratively-defined reasons.  You'll have to do the investigation and
determine what differences exist, which is responsible for the failure to
connect, and decide how to fix it.

Charles
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Charles Cazabon                                <qmail@xxxxxxxxxxxxxxxxxxxx>
GPL'ed software available at:         http://www.qcc.ca/~charlesc/software/
Read http://www.qcc.ca/~charlesc/writings/12-steps-to-qmail-list-bliss.html
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