Microsoft Exchange Connection Control : Exchange 2003

optimus_nz
optimus_nz used Ask the Experts™
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Hi,

I've turned on Connection Control in Ex2k3 to only accept mail from one server, our spam filters server. It seems like it took a while for DNS to propagate and some mail tried to route direct to our server as the previous MX record suggested.

My question is, when the connection control is locked down like this, does it still generate NDR's or another reply or does the email just get dropped?

Thanks
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Awarded 2009
Top Expert 2010

Commented:
It depends how the sending system is configured.

What will happen if they try to connect to your server then will be declined a connection.  This will then sit in their delivery system for 48 hours (depending in configuration) at which stage an NDR will be produced.

Depending on their mail system they will also receive delivery delayed message
If I understand you question.. if you put in the restrict to certain IP address of your other mail servers then when an IP address from another machine tries to connect the connection is just dropped.  Then after whatever timeout period the other server is set to (Use to be 5 days) then it will return a NDR itself to the sending user that it can't get ahold of you.  But in theory it should try again in a day or two and re-lookup your DNS information as long as it didn't have some very high TTL.
Alan HardistyCo-Owner
Top Expert 2011

Commented:
If your server is only configured to accept connections from specific IP Addresses - server that try to connect to your server will not make a connection and will not be able to send mail through.  They will retry and eventually give up.  If the MX records have been changed too, then they shoud eventally pick up on the changes and send the mail to the new MX records.
DNS usually takes anything from 24 - 72 hours to replicate around the world properly.  This is quite normal and you would have been better off leaving your IP address restrictions open for 2-3 days maximum then closing them off, but what is done is done.
If people cannot email you - they will either retry or call to ask if you have problems.
No NDR's will be sent from your server - but their server may send a delay message and then an NDR message if they cannot reach you at all.
Awarded 2009
Top Expert 2010

Commented:
We should start a choir! :-O
Alan HardistyCo-Owner
Top Expert 2011

Commented:
:-)

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