Freebsd, postfix and push email

Jonathan McKeown j.mckeown at
Tue Mar 30 09:14:09 UTC 2010

On Tuesday 30 March 2010 09:31:00 Matthew Seaman wrote:
> On 30/03/2010 03:01:27, Tim Judd wrote:
> > I've never heard of either, but when I configure my IMAP server and
> > put any mail client to it, as soon as a mail is delivered, the mail
> > client is notified.
> That's the IDLE extension to IMAPv4 -- it's not a push protocol as
> such: the client still has to log into the server rather than vice
> versa, but once the client has read all the available e-mail, it can
> put itself into an idle state, and the server will wake it up as soon
> as any new e-mail comes in.

Yes. In fact, one of the nice things about IMAPrev4 as a protocol is that the 
server is allowed (in fact, required by rfc3501) to notify the client if the 
mailbox size increases while executing any command, by sending an EXISTS 
response which the client is required to handle. IDLE is just a command that 
takes a long time to execute (specifically, until the client ends it or the 
server's time limit is reached) so that the server has to send EXISTS 
responses whenever mail comes in.


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