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Old 01-01-2010, 06:27 PM
Jerry Geis
 
Default one server handled sendmail added two more servers messes things up

Hi all,

I had one server running centos 4.7 i686 everything was fine with
incoming mail.

I now added two more servers centos 5.4 x86_64 and gave them machine
names all
part of the same domain as machine 1. I noticed that incoming emails are
being
round robined to all three machines. At this time I really just want
the one original machine
to handle my incoming email... The other two new machines are for other
purposes.

How do I tell the two new machines that all incoming email send to
machine 1.
Is there an easy way to do that? At this point I just turned off the two
new machines
and all mail is coming into the original machine just like before.

Thanks,

Jerry
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Old 01-01-2010, 06:35 PM
Les Mikesell
 
Default one server handled sendmail added two more servers messes things up

Jerry Geis wrote:
> Hi all,
>
> I had one server running centos 4.7 i686 everything was fine with
> incoming mail.
>
> I now added two more servers centos 5.4 x86_64 and gave them machine
> names all
> part of the same domain as machine 1. I noticed that incoming emails are
> being
> round robined to all three machines. At this time I really just want
> the one original machine
> to handle my incoming email... The other two new machines are for other
> purposes.
>
> How do I tell the two new machines that all incoming email send to
> machine 1.
> Is there an easy way to do that? At this point I just turned off the two
> new machines
> and all mail is coming into the original machine just like before.

This should be controlled by the DNS MX record for the domain name. Just set it
to the machine(s) you want to receive mail. If you want more than one to
receive mail but forward it all to one for delivery, set MAIL_HUB in the
sendmail.mc file on the ones that should forward (usually that's not necessary,
though).
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Old 01-01-2010, 07:05 PM
Jerry Geis
 
Default one server handled sendmail added two more servers messes things up

lists-centos wrote:
> What IPnumbers did you give the two new machines? What does your DNS
> look like.
>
> >From the outside, mail will be delivered to the MX- (or if that
> doesn't exist A-) record machine (based on the IPnumber in the DNS
> record) for the FQDN on the message.
>
> - Rick
>
> ------------ Original Message ------------
>
>> Date: Friday, January 01, 2010 02:27:12 PM -0500
>> From: Jerry Geis <geisj@pagestation.com>
>> To: CentOS ML <centos@centos.org>
>> Subject: [CentOS] one server handled sendmail added two more
>>
> servers messes things up
>
>> Hi all,
>>
>> I had one server running centos 4.7 i686 everything was fine with
>> incoming mail.
>>
>> I now added two more servers centos 5.4 x86_64 and gave them
>> machine names all
>> part of the same domain as machine 1. I noticed that incoming
>> emails are being
>> round robined to all three machines. At this time I really just
>> want the one original machine
>> to handle my incoming email... The other two new machines are for
>> other purposes.
>>
>> How do I tell the two new machines that all incoming email send to
>> machine 1.
>> Is there an easy way to do that? At this point I just turned off
>> the two new machines
>> and all mail is coming into the original machine just like before.
>>
>> Thanks,
>>
>> Jerry
>>
>



All three machines have the same FQDN.
something like A.mydomain.com, B.mydomain.com, C.mydomain.com

The IP numbers are X.Y.Z.170, .171 and .172

All three machines have MX records. they all have the same domain name.

It is a big deal to request changes from the provider so I was hoping
there was a way
to just tell the two new machines that incoming email to them just send
on over to the the
first machine.

Is there a way to do that - or am I going about this the wrong way?

Jerry

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Old 01-01-2010, 07:11 PM
Michel van Deventer
 
Default one server handled sendmail added two more servers messes things up

Hi,


> All three machines have the same FQDN.
> something like A.mydomain.com, B.mydomain.com, C.mydomain.com
No, they don't have the same fqdn, the fqdn includes the hostname.

>
> The IP numbers are X.Y.Z.170, .171 and .172
>
> All three machines have MX records. they all have the same domain name.
There's your error, the new one shouldn't have mx records for the domain
if they are not designed to accept mail for that domain.

>
> It is a big deal to request changes from the provider so I was hoping
> there was a way
> to just tell the two new machines that incoming email to them just send
> on over to the the
> first machine.
>
> Is there a way to do that - or am I going about this the wrong way?
There is a way but maybe there's a quicker (and dirtier) way. Just
reconfigure sendmail on the two new machines to *not* listen on the
public ip on the smtp port. Otherwise block port tcp/25 with iptables
(iptables -I INPUT -j REJECT -p tcp --dport 25)
But you should really get your DNS fixed.

regards,

Michel


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Old 01-01-2010, 07:19 PM
Jerry Geis
 
Default one server handled sendmail added two more servers messes things up

MAIL_HUB does the trick - thanks that was what I was looking for.

jerry

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Old 01-01-2010, 07:22 PM
John R Pierce
 
Default one server handled sendmail added two more servers messes things up

Jerry Geis wrote:
> MAIL_HUB does the trick - thanks that was what I was looking for.
>

you still should delete the extra MX records from the DNS


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Old 01-01-2010, 07:29 PM
Les Mikesell
 
Default one server handled sendmail added two more servers messes things up

Jerry Geis wrote:
>
>
> All three machines have the same FQDN.
> something like A.mydomain.com, B.mydomain.com, C.mydomain.com
>
> The IP numbers are X.Y.Z.170, .171 and .172
>
> All three machines have MX records. they all have the same domain name.
>
> It is a big deal to request changes from the provider so I was hoping
> there was a way
> to just tell the two new machines that incoming email to them just send
> on over to the the
> first machine.
>
> Is there a way to do that - or am I going about this the wrong way?
>

You can forward by setting MAIL_HUB but it may cause problems where you accept
mail at the rely, then reject at the delivery host because the user name is
wrong or from spam checkes. In that case, the intermediate host is required to
construct a bounce message and try to deliver it - and for spam it probably
won't be deliverable.

If you have some reasonably small number of users, you can make an alias file
that forwards each user to the fqdn of the delivery server. Or you can use a
virtuser table for the same purpose with a default reject rule.

Or, as someone else suggested, just stop sendmail or block port 25 on the one's
you don't want to work. Outside deliveries will retry each MX until one
succeeds, but it is slightly antisocial to knowingly make them do this extra work.


--
Les Mikesell
lesmikesell@gmail.com
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