I'm finally at the point where a SBS2003 network need to use Exchange for direct delivery of incoming mail. Nowadays it used pop3-connector to recieve mail from a webhosting company.
In this fascinating spam-world this causes a lot of error because mail are sended through another host than it first was recieved from..
This pop3-connector is big enough that I can't handle and control the risc of loosing delivery of incoming mail. I want to have the pop3-connector behave just like normal while Exchange operating just normal with direct delivery. How do I do?
I understand that I could,
1. Set our external IP as lowest MX record 10, then use the webhostings e-mail MX as 20. Which will carry the mail if our exchange server not responding.
2. I need to SAT/NAT/Accept open port 25 for incoming traffic in the firewall?
3. What do I (best practic/basic) need to do for security in this case of direct delivery, that our webhosting doing automatically today?
4. If I run the CEICW and select the Exchange for direct delivery, is pop3-connector still working as usual (if it got any mail from the webhosting)