Setting up POP3 and SMTP Relays with Exchange 2010

Wow, recently had SO much fun struggling with Exchange 2010, to set up a POP3 connectors for external mailboxes and an SMTP relay for an internal SQL mail server. The challenge was, that when I could relay internal mail to external, my POP mailboxes fell over, and vice versa...In the end, I had to delete all the connectors Exchange created by default, and set them up manually.

It all started when I was trying to send a SQL mail using CDO. I kept getting "-2147220977" error code, which translates into "0x8004020FL - The server rejected one or more recipient addresses" (Convert the code to hex, and look at TechNet for the meaning). When I rewrote my code to C# (.Net), it popped up with "5.7.1 Unable to relay". So, at this point, I was sure SMTP was the problem.

I deleted all the SMTP connectors, and recreated one for outgoing routing, and it worked... Or so I thought... even though the mail goes out, I now could not download any mail from POP3 mailboxes. When I started the POP3 download, Event log had an error event :"Cannot connect to the SMTP server 'localhost' on port 25. The error code was 0x800ccc0f. Verify that the Microsoft Exchange Transport service is running and that the Exchange receive connectors are properly configured"



Googling did not help much, as it seems not a lot of people have had this problem before, so out of desperation, I took to my trusty whiteboard, and designed what I wanted it to do (I know, such a developer thing to do, but hey, it worked). I came up with an action plan, executed it, and lo and behold, it worked.

This is what I did...

1. In the Exchange Management Console, go to Server Configuration, Hub Transport, and delete ALL receive connectors

Now let the fun start:

1. Using the Wizard, Create a new Connector, called "POP3 Mailbox Connector". Set the intended use to "Custom" and click on next
2. At Local Network Settings, remove the default, and add specific IP 127.0.0.1
   . For the FQDN, use the FQDN of the Exchange server, and click on next - This will tell the server which server to send the incoming mail to.
3. At Remote Network Settings, remove the default, and add "127.0.0.1". This will tell the server which machine will be doing the POP3 pickups. Click on next, and run through the confirmation screens (New, Finish)

At this point the connection is set, but because of security not set, it can't do anything

4. Double click on the new connection
5. Go to Authentication, and enable Basic Authentication only. This will allow the POP connector to send credentials to the remove POP mailbox server
6. Click on Permission Groups, and set Anonymous Users and Exchange Servers. This will let the current server connect to the boxes, either through the NW Server account or through and Exchange account
7. Click on Apply, and the POP3 component is set.


Now for the SMTP relay

1. Using the Wizard, Create a new Connector, called "SMTP Relay Connector". Set the intended use to "Custom" and click on next
2. At Local Network Settings, remove the default, and add the specific IP address of the exchange server
   for the FQDN, use the FQDN of the Exchange server, and click on next - This will tell the server which server to send the incoming mail to.
3. At Remote Network Settings, remove the default, and add the IP of the server you want to send emails from. Click on next, and run through the confirmation screens (New, Finish)

At this point the connection is set, but because of security not set, it can't do anything

4. Double click on the new connection
5. Click on Permission Groups, and set Exchange Servers. This will let the current server allow connections from the sending server
6. Go to Authentication, and enable Transport Layer Security (TLS) and Externally Secured. This will allow the server to receive the internally generated emails, and get the response from external domains
7. Click on Apply, and the SMTP component is set.

Now test, and there ya go... Hopefully this will make your searching simpler than what I had to go through to get it to work :)