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Can't access POP3 when in local area network

Posted on 2008-09-30
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Last Modified: 2013-12-23
I setup POP3 on my exchange server and I can access it when I am outside the building. But once I am inside the building, it can not connect to my pop3 account. I'm guessing this is a local dns setting but not sure where or how to add it.  I use a laptop and take it home with me each day.
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Question by:jimstringer
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Dimarc67 earned 50 total points
ID: 22609236
Assuming that you have a NAT firewall, you'll need to duplicate your external DNS records on the internal DNS server, but with the internal IP addresses instead of the public addresses.

Otherwise, your laptop will be trying to access your POP3 server using the public IP which is not generally possible from inside the network firewall.

For instance:
DNS 'A' record on public DNS:  mypopserver.mydomain.com........123.123.123.123
DNS 'A' record on private DNS (inside your firewall):  mypopserver.mydomain.com.......192.168.1.10

Hope this helps.

Dimarc67
New York, NY
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by:Steve
ID: 22612106
or... if its behind your firewall and NAT'd on an invalid address, why not simply do port forwarding on your router for POP3 to your mail server's IP address then you can just check mail from the public address..

so.. on router something like :

ip nat inside source static tcp <IP Address of mail server> interface <public interface (ethernet0) 25


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by:Steve
ID: 22612115
sorry i misread your post.. you CAN do it externally.. not internally.. Dimarc67's answer will work, or you could just set your POP3 to the internal IP address of the mail server..
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