Yesterday, Joe has called me. He asked me something about Email on mobile phones.

I think most people use Email just use 2 kinds of Emails:

1, POP3 for personal mails, or from ISP

2, Exchange, at work in office

When it comes across the difference between mail, exchange and blackberry, people are not sure. Well, I think many places you can find the information, but I can briefly describe here.

1, POP3 - POP3 is a protocol for a kind of mail server which will store your mails until you go to get it. It is like your home mailbox. If you go to get it, it will give you the letter by letter. You can delete it, but you cannot put anything back there.

2, IMAP - IMAP4, is something similar to POP3 but more intellegent, instead of just get mail by mail, you can ask what is in the mail or just get any attachment in the mail before you retreive the whole mail. Moreover, you can store any edited mail into the IMAP4 server as well.

3, Exchange - MS Exchange for mail is one part of MS office, you need to have a Exchange server situate in a domain, so that people inside the domain can exhange mails, contacts and calenders. Exchange user has to be domain users and inside the domain, that's the reason why you only can check company's exchange mail by logging into company's VPN.

4, Blackberry - it's Research In Motion proprietary product. Similar to Exchange, it integrates with operator or corperate mail servers so that users can get mails through a operator defined tunnel (APN).

Blackberry was created for mobile mails, because the way it encoded/encrypted the mail makes the maili transferrable even in 2G environment. Moreover, it is the first mobile push mail device (immitating Exchange), by always listening to server for new mails. Because of encryption and the hassle of dedicated tunnel from operator to blackberry server, people always say Blackberry is the most secured mobile mail.

However, as POP3 can also be transferred in a secured way, I guess the good think about blackberry is push function and dedicated channel, as in 911, all people in NYC cannot get the phone call but that time blackberry is still working as mobile jamming won't affect the APN for blackberry (of course when the APN for blackberry is overloaded, the QoS of blackberry can also be that worse).

With the needs of cheap push mail, IMAP has en extension, IMAP IDLE allow clients to keep connection to IMAP server open and when there is new mail, then the IMAP server woudl tell the client.

Indeed, listening port for push mail is not a good method for mobile, as the air resources is very expensive and by default, mobile has a very good push channel, which is SMS. Therefore, OMA has developed Mail Notification, which allows operators to send a special SMS (or IP push message) to client to alert the arrival of new mails.

It works nicely and for mobile operator, it is a cheap way to do. However, as everyone has so many email addresses, how can legacy mail server generates SMS push notification to mobile users is a challenge and blackberry, as the leader of this area is also facing a challenge, if MS Exchange would work on mobile directly, then coperate users so not need blackberry to check mails.