Push email utilizes a mail delivery system with real-time capability to “push” email through to the client as soon as it arrives, rather than requiring the client to poll and collect or pull mail manually. With a push email smartphone, for example, the client’s mailbox is constantly updated with arriving email without user intervention. Smartphones announce new mail arrival with an alert.

Push email differs from conventional email systems that are “pull” oriented. Usually, when email is sent, it arrives at the recipient’s Internet Service Provider’s (ISP’s) mail server, where it is held for collection. It might instead arrive at a website server, if the email is Web-based. Either way, email remains on the mail server until the recipient uses an emailprogram to poll the mail server. If new mail is present, the email client “pulls” the mail to the client’s computer. The difference between this scheme and push email is that, with push email, the mail is pushed through to the client without waiting for polling.

Push email can be somewhat simulated using an email client set to frequently poll for new mail. However, this requires the email client to be open and running and is less efficient. Polling involves “handshaking” between the client software and the mail server. If the server is busy, the delay in completing the handshake can lengthen, causing the client to time out.

Therefore, polling should not be set so frequently as to cause premature time out errors. To prevent this, one must increase the delay between polling times. In many cases, a minute or two delay between “pull email” and push emailschemes may not matter, but in some cases, a minute can make all the difference. Push email can be especially crucial to field reporters, stock market businessmen and other professionals for whom time is of the essence. A one-minute delay can make all the difference in breaking a story, losing money, or making a crucial sale.

BlackBerry was the first personal digital assistant (PDA) to offer push email and gained near-instant success as a result. Today, many devices have incorporated push email, and its popularity continues to grow. Some of the products that have incorporated push email include Chatteremail for Treo, Nokia Intellisync Wireless Email, Roadsync, and Sony Ericsson phones.

[original posted by Wise Geek]