exchange email?

David Ford david at
Sun Jan 21 17:21:50 CET 2007

The term "Push email" comes from a client signing on to the server and 
issuing a "look for ..." instruction to the server.  Also known as 
idling or long-delay poll.

The logic of it is to have the client only issue new "look for ..." 
instructions when those instructions change, and until the client 
disconnects, the server should send "i have new ..." responses whenever 
it figures out there is new mail.  Following that, the client says 
"gimme" and all are happy.

The only problem with this is NAT traversal where a busy firewall ages 
the oldest idle connections.  To combat this, developers make the client 
issue "look for ..." rather frequently if such behavior is discovered.  
Some developers however just play the safe route and always issue the 
"look for ..." instructions periodically.

In effect, the logic of this isn't really changed from the original 
design.  It's just done a bit differently.  Some of it is really just 
the marketing aspect.  Aunt Millie doesn't grok the protocol.  She just 
sees the "new feature!" printed boldly on a high priced M$ product box :)

The only truth in advertising, is that there is rarely truth in advertising.


David Schlesinger wrote:
> >Microsoft "push email" isn't push at all.  If you read the
> >specifications, it's just another method of polling a server to
> >determine if and what segments of new content is ready for transfer.
> I think this is true for the "Outlook Web Access" interface which, for 
> instance, Evolution (and Pocket Outlook on Windows Mobile 5!) use. 
> There's some sort of back-end interface which Outlook 2003 and 
> Entourage can take advantage of with an Outlook Server; I'm not sure 
> whether whatever they do there qualifies as "true push email" or not...

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