Quote Originally Posted by EricaJ1073 View Post
BIS is push email also. It's pushed to your device.
Yes, but it isn't pushed directly from the mail server to the RIM infrastructure. A BIS infrastructure server checks your mail account on your behalf at a variable interval, which can be as little as 1 minute if you've been sending and receiving recently, or as much as 15 minutes if you've been idle. (This is clever, as it gives the user the impression of relatively low latency at the times when they'd be likely to notice it - i.e. when engaged in near-realtime "conversations" - but conserves server resources when the device is idle anyway.)

There's also been a rumor around for quite some time that RIM will finally support the IMAP IDLE extension in a new BIS release in the near future, which - assuming the IMAP server supports IDLE - would effectively provide a push-like experience to the user, much like Exchange does to Outlook clients and BES. It's actually interesting that they haven't already chosen to do this (perhaps they fear that if RFC 2177 catches on, their push-mail "secret sauce" will eventually become an open-standard commodity, cutting into revenues for the BES stack of products).