Concepts - How it All Works

The Microsoft SMTP Part

As mentioned, the SMTP server delivers your email on the Internet if you have an Internet connection and can use the services of a name server (name resolution). When you click Send, your client email program (Outlook Express or something similar) contacts your SMTP server and passes it the message. The SMTP server contacts the SMTP server of the destination domain and negotiates to deliver it there. All the mail that your SMTP server receives is placed in a drop folder. That's the end of the SMTP servers delivery loop.

The Name Resolution Part

You can receive mail from the Internet if you have a domain name and a MX (Mail eXchange) record in your domain zone record. When there is mail to be delivered to your domain, the sending SMTP server first contacts a name server to find out which computer in your domain is responsible for mail deliveries. This is called name resolution. If this information is available, it then contacts your SMTP server.

You Internet Service Provider (ISP) will usually supply name resolution services for a small fee. You can also use HOSTS files or NETBIOS names for name resolution if your mail system is a small network that is not connected to the Internet.

The IMS POP3 Part

When you want to check for email messages, your client program (Outlook Express or something similar) contacts your POP3 server. The POP3 server checks the drop directory to see if you have any mail waiting in there and delivers it to you if there is.

The POP Agent

If the SMTP server and the POP3 server are from the same package, this all works seamlessly. However, in this setup, the IMS POP3 server is not looking in the Microsoft SMTP server's drop directory for the messages. It expects them in a different directories structure. This is where the POPAgent service comes in. It takes the messages out of the Microsoft SMTP drop directory and places them where the IMS POP3 server can find them.