[BlueOnyx:11100] Re: Blueonyx Digest, Vol 43, Issue 37

[Chad Bersche]

Dan:

Thank you for this.  Let me see if I can clarify what I'm seeing a bit.  
Let's call the two domains I'm dealing with "mydomain.com" and 
"ispdomain.com".  For my DNS entries from my DNS provider, I have an 
entry for "mx.mydomain.com".  That's fine, and is what I want to be used 
when someone tries to send me email to 'myuser at mydomain.com'. The 
incoming email gets routed thru the host specified by "mx.mydomain.com" 
and gets de-spammed, etc.

However, on my blueonyx system, I must send email out thru 
"mail.ispdomain.com".  I've specified this in the GUI, and have 
validated that it's in the proper sendmail.cf files as one would expect:

# "Smart" relay host (may be null)
DSmail.ispdomain.com

However, when you look at my outgoing mail logs I see this (domains and 
users obfuscated):

Aug  3 12:04:03 blueonyx sendmail[26976]: q73H42FA026974: 
to=<someone at somewhere.domain.com>, ctladdr=<user at mydomain.com> 
(503/501), delay=00:00:01, xdelay=00:00:01, mailer=relay, pri=233271, 
relay=mx.mydomain.com. [aaa.bbb.ccc.ddd], dsn=2.0.0, stat=Sent (Message 
received: 20120803170403.MXVD12025.mta.ispdomain.com at imp09 E0000)

To me, it is unclear why I have a Smart Relay Host set to 
mail.ispdomain.com, but clearly in the message delivery logs I see that 
the relay that's being used is mx.mydomain.com.  This makes no sense to 
me, and I have no idea why it would disregard the smart relay setting....

This previously was not a problem, as there was no explicit MX record 
for mydomain.com, but mail was still routed to the same IP as 
mx.mydomain.com currently points to.

So, why might sendmail be disregarding mail.ispdomain.com smart relay, 
and substitute mx.mydomain.com instead?  For a total hack, I've added an 
entry to my (internal) DNS that points mx.mydomain.com to the IP address 
of mail.ispdomain.com, but that's a total hack, and shouldn't be necessary.

Again, all help happy welcomed!

Thanks!


On 7/31/2012 1:39 AM, blueonyx-request at mail.blueonyx.it wrote:
> Message: 4
> Date: Mon, 30 Jul 2012 23:09:26 +0100
> From: Dogsbody <dan at dogsbody.org>
> Subject: [BlueOnyx:11049] Re: Why does mx record override Smart Relay
> 	host?
> To: BlueOnyx General Mailing List <blueonyx at mail.blueonyx.it>
> Message-ID: <50170616.901 at dogsbody.org>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>
> Apologies if you know this but it isn't clear from your message so I
> want to check...
>
> A smart relay uses MX records.  A lot of people don't know this and in
> some cases an A record can work but it is designed for and is supposed
> to use MX records.
>
> If you need to use mx.example.com for something else then use whatever
> you like (smarthost.example.com) as the smarthost entries and change it
> in the GUI.
>
> It's actually really handy being able to use MX records for the
> smarthost as you can use the priority values to create backups so there
> isn't a single point of failure.
>
> Dan
>
> On 30/07/2012 20:17, Chad Bersche wrote:
>> I recently updated my DNS provider, and as part of that update, the DNS
>> provider created mx host entries (i.e. mx.domainname.com) that pointed
>> to their mail forwarding service (which I do use).  However, the odd
>> thing is that after this happened, I noticed in my outgoing mail log
>> that the relay host is now using mx.domainname.com rather than the Smart
>> Relay host that I had set up (and which I want outgoing mail routed
>> through at my ISP).
>>
>> Why is sendmail using relay=mx.domainname.com (in maillog) when a
>> different Smart Relay host has been set up?  This seems incorrect,
>> especially since I have specified a smart relay host.  I've hacked
>> around it for right now with a local DNS entry that points
>> mx.domainname.com to the IP address of my smart relay host, but that's a
>> true hack, and one that I don't think I should have to make.  I also
>> need to keep the mx.domainname.com entries in my DNS so that my external
>> mail fowarding/spam filter can process the mail before it routes to me...