The way Internet mail currently works, subscribers to an ISP get their mail via POP3. The mail transfer is initiated by the subscriber's computer, which acts as the POP3 client. There is no way for the ISP's mail server to notify the subscriber that he has mail. Instead, the subscriber's computer must poll the mail server. Some subscribers set their computer to poll the mail server every 10 minutes, but there is no restriction, and a subscriber could poll the mail server as frequently as he wants. If every subscriber sets their computer to poll the mail server every 10 minutes that could start to put a real strain on the mail server. This could become a bigger problem with always-on Internet service. The POP3 protocol is good for a subscriber on a dial-up account who needs to connect to the Internet, get his mail, and get off. It's very inefficient for always-on Internet connections.
So, how about this idea: a protocol where either side can initiate the transfer of mail. This already exists in SMTP as an extension (ETRN). Many (or most?) cable modem companies prohibit subscribers from running a mail server. Will this change in the future?
Note: It gets even worse with IMAP4. Some IMAP4 clients open a connection and keep it open for hours at a time. Polling is one thing. Opening a connection and keeping it open for a long time is much worse. Subscribers should be running IMAP4 servers on their home network, and their mail should be delivered by SMTP from the ISP's mail server.
Posted by Doug Sauder at July 25, 2002 09:42 AM