[cobalt-users] MX Records and Site Moving

[Cobalt List <cobalt@xxxxxxxxxxxxxxxxxxxxxxx>]

Hi All,

As long as the DNS gurus are still out there lurking I encountered an 
interesting problem recently that I still haven't yet figured out what 
caused it.

The scenario is this:
--I've got a client who wants to move their website from their current host 
to my server. -- Great.

My usual procedure is: setup the site and DNS on my box, submit the 
nameserver change and wait for the info to update -- in my experience this 
takes 24-48 hrs for everyone to update to the new nameservers.  This can 
take even longer if the DNS info is cached. This stinks because meanwhile 
they have to check two different mail accounts until everyone is updated.

So I thought I'd do something slick:
I setup the virtual site on my box, and the DNS.  I  had the A records 
point to their old hosts IP addy and the MX records point to their old mail 
servers.  I also set the TTL on the record to something like 300 seconds.

So I ran a dig against the old host's nameservers using the clients 
domain.  Got the A records and the MX record information -- they had two 
mail servers one with higher priority than the other.

I setup the DNS on my box with the high priority mailserver only (BTW, i 
did verify that the high priority mailserver at the old host was up and 
running.) and had the A records pointing to the old IP.  My intention was 
to wait a few days for the nameserver info to update and then switch the 
DNS info point to my IP's and mailservers, since I've  got the TTL turned 
down, the switch should then only take 5 minutes to be active everywhere.

Well the nameservers switched and ....bingo...website is still coming off 
the old host but....no mail --- Yikes!  When I say no mail, I mean no mail 
in the old place and no mail on my server either -- it's all floating 
somewhere in internet limbo.

The client calls in a panic saying they haven't recieved mail in 24 
hrs.  So I quickly switch the MX back to my box...bingo all the mail from 
the last 24 hours hits my box in about 15 minutes.

What the hell happened?

Brian