In wp7 email account settings if u are using hotmail u will see this setting " as items arrive" . This is the true push technology . This is MS new "Direct Push technology" and it saves battery life by not initiating connections everytime the phone is set to check email in time intervals. It maintains an open connection to hotmail . Direct push only works in Hotmail in wp7 and not yahoo, google or other accounts which will use the older iphone style time interval push email.
this is how it works. What they mean by in open connection is through a unique identifier. this does not drains battery...as no data flow is taking place all the time. only yr Data connection is alive as per usual and even when its sleeping or idling, the phone receives info from Hotmail because hotmail knows where to send this info.
its like a pipe connected from A (phone) to B (hotmail) but no water flowing unless there is a need to.When u have a water to flow, B sends out a "trickle" to A to open up and establish contact and the water flows through. all this is through a unique identifier which B uses on the network . in addition the phone ( A) also periodically sends out trickles to B after studying network conditions. So direct push adjusts to any network conditions when sending out email.
As with time based intervals, the phone from A will connect to B and retrieve the water. with B having no part in it or being uncooperative not to waste A;s time even when there is no water..So if u set the wp7 time interval , u not only dont get timely emails but also wastage process as each time the phone will try to establish the connection again . There is no unique identifier involved. if for some reason the phone could not establish a connection , it try again and again in a loop and eventually returns an error, this has been seen with wp7 time based push repeatedly as an error pops out. and the email will not synchronize again at the next time interval and states " attention required". this means push email in the phone stops workig altogether because something at the other side has changed or expereicning problem
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