(with apologies to Cricket Liu)
Okay...we have 3 mail servers, with preferences set as 10, 20 and 30
respectively. Our primary mail server (Greeley) is down, but the other 2
(Fort.Collins, Denver) are running...
Now...let's pretend we're an airline passenger (an email message) trying
to get to Greeley, Colorado (which we know as KewlHomeTown). There isn't
a direct flight (it's down remember?) so we have to fly to either
Fort.Collins, or Denver. Okay, consulting my trusty atlas, I see that
Fort.Collins is closer to Greeley than Denver so we buy a ticket to
Fort.Collins.
Arriving there, we now have a choice...we can try get a flight to
Greeley, or we can fly to Denver THEN Greeley. Since flying AWAY from
our destination is way dumb, we stroll over to the ticket counter to see
if there's a flight to Greeley anytime soon...
"Say Miss ah...Tiffany...could ya sell me a ticket to KewlHomeTown
please?", we say in this really nonchalant, frequent-traveller kinda
manner.
"Say what...?", the ticket clerk says, motioning the security guard over
(she's just seen Con Air on home video and you look just like M.C.
"Swamp Thing" Gainey).
Here's the "gotcha" > most mailers will ONLY look for their local host's
CANONICAL domain name in the list of MX records. They don't check for
aliases (domain names on the left of CNAME records).
Unless you ALWAYS use canonical names in your MX records, there's no
guarantee a mailer will be able to find itself in the MX list, and
you'll run the risk of having your mail loop. If you send mail addressed
to a particular domain name to a mailer that isn't configured to accept
mail for that domain name, and it finds itself as the most preferred
mail exchanger, it may bounce the mail. The hosts you list as mail
exchangers MUST have address records because a mailer needs to find an
address for each mail exchanger you name, or else it can't attempt
delivery there......
*whew*
/wiZZ
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: 08 February 2000 09:48
Subject: Re: [IMail Forum] IMail Troubles (?)
> Why should a CNAME never be used in an MX record? Why can't the CNAME
point
> to the A record?
>
> Just trying to learn....
>
>
> Don
>
> -----Original Message-----
> From: Peter Salvage <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
> Date: Tuesday, February 08, 2000 7:08 AM
> Subject: Re: [IMail Forum] IMail Troubles (?)
>
>
> >hmmmm
> >
> >You have mega-problems with your DNS :-)
> >
> >I would start "fixing" there first, then try iMail again. I've listed
> >the errors below, but briefly, your name servers that respond to a
dig
> >request are different to the name servers listed as authoritative for
> >your zone by Network Solutions. Also, your MX records are wrong. You
> >should NEVER use a CName Record for an MX Record. Always always
always
> >use an A Record.
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