This is a question about DNS records and MX records and how I'm getting some 
weird behavior.  It's not strictly speaking Declude issue, but I have a lot of 
respect for the people that used to hang out here and I'm hoping there's 
someone around who can give me some insights.

Original problem:
We use Comcast for our upstream provider.  A few years ago, when we switched to 
them from our telecom provider, they told us that their DNS servers would 
sometimes intercept DNS calls even though we have our own DNS server.  This was 
supposedly because we only rent a small IP subnet from them.  At the time, they 
had us send copies of our zone records to them so that their DNS  servers would 
have the same information as our DNS server.  This worked fine until this fall, 
when we installed a new mail server on a new IP address.  Our DNS server, of 
course, was updated to reflect this change.  However, mail sometimes shows up 
at the old mail server anyway, in a more or less random pattern.

It apprears to me that most of the time when people send mail to us, their mail 
servers correctly getting the IP address resolved by our DNS server.  However, 
about 25% of the time, it appears that the DNS request from those sending mail 
servers receives an outdated response from some unidentified Comcast DNS 
server, resulting in the wrong IP address and the mail ends up going to our old 
mail server.

Suppose, for example, that you send a message to imailad...@bcwebhost.net (the 
address I'm using here, which is a misnomer since our new mail server is 
running SmarterMail).  The MX records for bcwebhost.net points to 
mail.bcwebhost.net and the A record mail.bcwebhost.net points to our new server 
IP (ending in .200).  So your email should arrive at our new mail server.  
However, sometimes it will arrive at the old mail server named 
mail2.bcwebhost.net (IP ending in .193).  The old DNS records had the 
bcwebhost.net MX record pointing to mail2.bcwebhost.net, for which the A record 
pointed to .193 (the old server).

I've been going in circles for about a month with Comcast on this and they 
don't recall that they're the ones who told me three years ago that they 
sometimes intercept DNS calls.  I was wondering if anyone has any ideas or 
suggestions on how to track down the errant DNS calls?

Second problem:
In our new DNS records, I have it set up something like this:

two MX records:
bcwebhost.net MX mail.bcwebhost.net
mail.bcwebhost.net MX mail.bcwebhost.net

one A record:
mail.bcwebhost.net A (IP.200)

Is there any reason I can't have the same name for both an MX and an A record 
(in this case, mail.bcwebhost.net)? The Comcast people claimed this was wrong 
and that the MX record should point to an IP address directly instead of a host 
name (which I'm sure is wrong).

They tried to claim that this is the cause of my original problem but even if 
they're right about this, then it still doesn't explain the original problem.



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