Freebsd, postfix and push email

Dan Nelson dnelson at
Sun Mar 28 20:38:54 UTC 2010

In the last episode (Mar 28), Ron said:
> Jeffrey Goldberg wrote:
> > On Mar 28, 2010, at 1:36 AM, perryh at wrote:
> >> Er, no.  POP3 and IMAP are "pull" services, wherein the client polls
> >> the server periodically for any newly-arrived messages.
> > 
> > IMAP, but not POP3, can be used to push, but the iPhone mail client
> > doesn't support that as far as I know.  It does support being pushed to
> > over Mobile Me, but not on regular IMAP.
> So how is Mobil Me and Exchange Servers (MS, Zimbra, etc) doing it? 
> That's what I'd like to replicate on my FreeBsd server.  This seems to be
> a well guarded secret I'd like to crack.
> On the iPhone, at least, the phone is not polling the servers, some kind
> of message (SMS?) is being sent to the phone that makes it put a little
> red badge on the corner of the mail app icon telling it how many messages
> are waiting.  The messages don't seem to be download during the push, it's
> just a count (I could be wrong about this).

For ActiveSync at least, the phone has to keep a TCP connection to the
server open 24/7, and the server sends a notification when a new mail
arrives.  MobileMe probably works the same way.  The IMAP protocol supports
a similar "notify on new mail" option, but for some reason Apple doesn't use
it in their client.

	Dan Nelson
	dnelson at

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