Mailing List SIMS@mail.stalker.com Message #5638
From: Bill Cole <listbill@scconsult.com>
Subject: Re: Backup mailer
Date: Sat, 25 Mar 2000 14:50:14 -0500
To: SIMS Discussions <SIMS@mail.stalker.com>
At 11:38 AM -0500 3/25/00, billc@greenbuilder.com wrote:


> Aaron Lynch <aaron@digitalspeed.com> writes:
>
> >because your server is still mail.yourdomain.com, not domain1.com, which
> >is down or not responding.  You are right though, you need mx records
> >
> >mx 10 mail.domain1.com
> >mx 20 mail.yourdomain.com
> >
> >strictly speaking you don't even have to have the router entry
>
> Sorry, but I'm still not getting it.
>
> To clarify:
>
> Let's say I have two mail servers:  Server1 and Server2.  Server2 is to be
> set up as the backup machine.
>
> I have mail for a number of domains coming in to Server1:
>
> mydomain.com
> domain1.com
> domain2.com
> etc.
>
> My MX records are presently
>
> mydomain.com MX 10 mail.mydomain.com
> mail.mydomain.com A xxx.xxx.xxx.1
>
> domain1.com MX 10 mail.domain1.com
> mail.domain1.com C mail.mydomain.com
>
> domain2.com MX 10 mail.domain2.com
> mail.domain2.com C mail.mydomain.com


Are those 'C's indicating CNAME records?

That's bad. Never point an MX at a CNAME. Half the net won't understand,
and the rest shouldn't. It's *WRONG*

If you really fee the need to have the mail.domainx.com names exist, make
them A records. There is no harm in having multiple names' A records share
an address.

> It sounds like you're saying to change the records on domain1.com etc to
>show:
>
> domain1.com MX 10 mail.domain1.com
> domain1.com MX 20 mail.mydomain.com
> mail.domain1.com C mail.mydomain.com
>
> domain2.com MX 10 mail.domain2.com
> domain2.com MX 20 mail.mydomain.com
> mail.domain2.com C mail.mydomain.com
>
>
> I can see where that would work if I didn't have the CNAME records already
> pointing to mail.mydomain.com.

Well, you shouldn't anyway.

Besides, what good would it do you to have the backup mail server just
another name for the primary?  The do need to be actual seperate machines
or there is no point.


>
> The only way that I can see it working would be to have the secondary
> server be something like mail2.mydomain.com:
>
> mydomain.com MX 10 mail.mydomain.com
> mydomain.com MX 20 mail2.mydomain.com
> mail.mydomain.com A xxx.xxx.xxx.1
> mail2.mydomain.com A xxx.xxx.xxx.2

Yes.


> and then have the other domains like this:
>
> domain1.com MX 10 mail.domain1.com
> domain1.com MX 20 mail2.mydomain.com
> mail.domain1.com C mail.mydomain.com
>
> domain2.com MX 10 mail.domain2.com
> domain2.com MX 20 mail2.mydomain.com
> mail.domain2.com C mail.mydomain.com
>
> and then have it set up with the router entries:
>
> mydomain.com = mydomain.com.smtp
> domain1.com = domain1.com.smtp
> etc
>
> Am I missing anthing crucial here?  Is there an easier way to do this?

Yes. Lose the CNAME records. They are useless.

If you MUST have them for some other reason, still make sure you don't
have MX records pointing at the CNAME names. That is bad. It is counter to
the DNS spec. It is unnecessary. Don't do it. It breaks things.


> Of course, what I'd REALLY like is a mirror server that clients could
> download their mail from in the event that Server1 goes down, but since
> that is fortunately quite rare these days (v 1.8b8), it's not as pressing
> an issue as it once was.  Of course, such a mirror server would have to
> receive new mail if Server1 goes down AND there would have to be a
> mechanism in place to update Server1's account records once it came back
> up, to cover for the inevitiable addition/subtraction of individual pieces
> of mail from Server2 while Server1 was down.  I realize that this might be
> a pretty tall order, but it's definitely on my wish list.


That's an extremely tall order if you want it to really work right and
automatically. I don't expect the basic pieces neessary to ever appear in
SIMS. You might be able to cobble something up with Communigate, but even
then you are looking at a significant amount of work to rig the system up.


--
Bill Cole



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