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Date:      Mon, 1 Feb 1999 06:43:04 -0800
From:      Don Lewis <Don.Lewis@tsc.tdk.com>
To:        "Jasper O'Malley" <jooji@webnology.com>, John Saunders <john.saunders@nlc.net.au>
Cc:        phil grainger <thi226@iname.com>, freebsd-isp@FreeBSD.ORG
Subject:   Re: help wanted!
Message-ID:  <199902011443.GAA08735@salsa.gv.tsc.tdk.com>
In-Reply-To: "Jasper O'Malley" <jooji@webnology.com> "Re: help wanted!" (Feb  1,  7:13am)

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On Feb 1,  7:13am, "Jasper O'Malley" wrote:
} Subject: Re: help wanted!
} On 1 Feb 1999, John Saunders wrote:
} 
} > It's also a good idea to create a bunch of CNAMES (aliases) in the DNS
} > so it looks like you have 1 service per host, then direct the service
} > to the host it is on. This lets you move things around without disturbing
} > users. e.g.
} > 	ns1.domain.com.au		primary name server
} > 	ns2.domain.com.au		secondary name server
} 
} Let me just point out that using a CNAME for a name server address is a
} no-no. Only one DNS resource record type can refer to a CNAME in its data
} field, and that's a CNAME itself. The same deal applies to MX records
} (can't point to a CNAME), so mail.domain.com.au probably shouldn't be a
} CNAME, either. Use redundant A records, instead. With that caveat, I
} wholeheartedly agree with John's suggestion.

Since the name that the the MX record points to is local to your DNS
zone, it's easier to just point the MX at the actual host that's handling
incoming SMTP.  Instead of:

domain.com.au.		IN	MX 0	mail.domain.com.au.
mail.domain.com.au.	IN	A	192.1.1.1
foo-host.domain.com.au.	IN	A	192.1.1.1

just do:

domain.com.au.		IN	MX 0	foo-host.domain.com.au.
foo-host.domain.com.au.	IN	A	192.1.1.1

That way you don't have to teach the MTA on foo-host that it's name is
also "mail.domain.com.au", and if you want to change the IP address
of foo-host, you only have to change it in one place.  This also makes
the SMTP greeting that your mail server spits out (foo-host.domain.com.au)
consistent with its DNS name that you get by following the MX.

If you want to switch your mail host to another server, you only have to
change the MX.

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