Push email utilizes an email delivery system that has the 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 — email manually. This technology is often used with smartphones. With a push email smartphone, the client’s mailbox is constantly updated with arriving email without his or her intervention. These smartphones announce the new mail's arrival with an alert.
This type of email delivery system differs from are pull-oriented systems. 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, or it might instead arrive at a website server, if the email is Internet-based. Either way, the email remains on the mail server until the recipient uses an email program to poll the mail server by using an email polling protocol, such as Post Office Protocol (POP3). If new mail is present, the email client downloads the emails onto the client’s computer. The difference between this scheme and push email is that, with push email, the email is sent to the client without waiting for polling.
Push email can be somewhat simulated by setting an email client to frequently poll for new mail. This requires the email client to be open and running, however, so it is less efficient. Polling involves electronic 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, a user should increase the delay between polling times. In many cases, a minute or two delay between pull and push schemes might not matter, but in some cases, a minute can a big difference. Push email can be especially crucial to field reporters, stock market businessmen and other professionals for whom emails can be urgent. A one-minute delay can make the difference when it comes to breaking a story, making money or completing a crucial sale.