MX Record Confusion

[Barry Margolin]

In article <9j8b69$d4e at pub3.rc.vix.com>, chriskk <chriskk at pixi.com> wrote:
>I need to change email servers from our inhouse Linux/Sendmail server
>to a outsourced email provider. I understand that the MX records need
>to be changed, but not sure what new settings will be correct. Hoping
>the transition to go smoothly with no email loss and little to no
>disruption to the users.
>
>Current situation:
>inhouse Linux/Sendmail server(serverA) setup w/ 13 email accounts all
>working.
>Oursource email provider(serverB) setup w/ exact same 13 email
>accounts.
>All client computers setup with both email accounts.
>
>Confusion:
>Do I just change the MX record to point to the new serverB and after
>the change propagates through the net remove serverA settings from
>client computers. Then delete user/email accounts from serverA.

Yes.

>Have 2 MX records such as
>IN  MX 10 serverB(new)
>IN  MX 20 serverA(old)
>And after the new settings propogate through the net remove serverA MX
>.. remove serverA client settings and delete accounts on server.

You would use this technique if serverB weren't running yet.  Senders would
try to send there, but when the connection fails they would fall back to
serverA.  Then after the DNS change propagates you would start serverB and
everyone would switch over.  This is a way to make the change smoother, but
it probably won't work if serverB is an outsource site that's shared with
other customers of theirs, since they can't shut down the server to wait
for your change to propagate.

>To add to my confusion :
>serverA is used as the sending server for an email newsletter and
>still would be used for the same purpose.

Irrelevant.  Outgoing and incoming mail are totally unrelated.

-- 
Barry Margolin, barmar at genuity.net
Genuity, Burlington, MA
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