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I have an Exchange server (not configured by me) with 3 receive connectors: Client, Default and "My internet connector". The server has one IP=192.168.255.1

Default -> bind: 0.0.0.0:25, :::25; Permission groups: Anonymous/Exchange users, Exchange servers, Legacy Exchange servers

My internet connector -> bind: 192.168.255.1:25; Permission groups: Anonymous/Exchange users, Exchange servers, Legacy Exchange servers

They both have the same FQDN: MYSERVER.DOMAIN.COM

I've disabled "Anonymous exchange users" from Default connector, and sending an email from Gamil fails with "server requires authentication". So, it's using Default connector to receive from the internet

Question: How does Exchange select a receive connector? How can I make it use "My internet connector" to receive inbound mail from the Internet?

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2 Answers 2

The 0.0.0.0 bind on Default is taking port 25 on all addresses (0.0.0.0), which should be forcing the port bind on My internet connector to fail.

To get it to take over, you'd want to drop the 0.0.0.0 bind out of Default, and give 0.0.0.0 to My internet connector. Or leave it as is with the specific IP bound, but make sure that if it has multiple IPs, that it's bound to the one that's actually getting the mail.

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That makes sense. Yet, in order to be 100% sure, i've configured a test server with the same characteristics as the one i described above (1 NIC, 2 connectors). In this case, the connector that receives the communication on 25 by default is "My internet connector" instead of "Default" as needed, eventhough running Netstat on the server displays "0.0.0.0:25" ???? (i've changed the FQDN of each connector and i used telnet in order to know which connector exchange was using to answer requests on port 25 . Any ideas? –  user59009 May 9 '11 at 12:19
    
The process binds 0.0.0.0:25 even if it's only set to listen on a specific address. –  Shane Madden May 9 '11 at 17:55

When it comes to deciding which Receive Connector to use it is basically the most specific one that wins.

This makes the Remote IP Address range on the Network tab important.

The Default Receive Connector has a default range of 0.0.0.0-255.255.255.255 (ie "anything") to receive mail from. Your "My Internet Connector" one probably has the same.

So Exchange doesn't know which one is should be using if there are no other clues to tell it. You need to be more specific in your Receive Connector configs so that it can make the decision correctly.

So you can fix this one of two ways: 1) Add a second IP address to the HT server, and bind the Default Receive Connector to the primary IP and the "My Internet Connector" to the secondary IP, then make sure incoming SMTP is NATed to the secondary IP only.

2) On the Default Receive Connector, remove the default IP ranges and specify your internal subnets only.

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