[Dovecot] blackberry with imap idle and concurrent connections

[Bill Cole]

At 12:11 AM -0600 9/26/07, Chris Tirpak wrote:
>Hello -
>
>I've combed the wiki and archives a bit and can't seem to find what I am
>lookng for. It seems that BlackBerry Internet server has an issue with IMAP
>accounts along with IDLE and concurrent connections. Please see the
>following link (sorry it's fairly long):
>http://www.blackberry.com/btsc/search.do?cmd=displayKC&docType=kc&externalId=KB13846&sliceId=SAL_Public&dialogID=53398271&stateId=0%200%2027265273
>
>It appears as though IDLE can be implemented without "concurrent
>connections". Courier appears to do this although they have an option to
>turn it on. At first blush it seems obvious that any mail server will permit
>concurrent connections but as I read the docs for Courier and BlackBerry it
>appears to be a subtle thing whereby IDLE allows more than one connection to
>IDLE against the same IMAP folder when using maildir.
>
>Does Dovecot support his? Also, if anyone on the list has experience running
>a BlackBerry against Dovecot, are you currently getting instant (or near
>instant) notifications? If so what service are you using? T-Mobile?
>
>I am considering upgrading and using Dovecot but BlackBerry support has
>become critical.
>
>Thanks in advance.


I have just confirmed with a direct test that Dovecot 1.0.0 using 
Maildir does properly service 2 simultaneous IDLE sessions on the 
INBOX. I've got my Palm ChatterEmail client logged in and idling and 
have a manual IMAP session (telnet localhost 143...) and the messages 
are popping up on the Palm in lockstep with the 'EXISTS' messages 
kicking out on the telnet session. Meanwhile, Eudora is doing its 
things from my Mac against the same mailbox (actually tossing 
messages out of INBOX to other folders) and I'm pretty sure I left 
Outlook running on my office machine and looking at the same mailbox, 
so whatever flaky stuff it does is happening on whatever schedule it 
uses as well...

Note that one strong consideration for IMAP servers with more than a 
handful of users is going to be dealing with the high concurrency of 
a lot of eternal connections from the Blackberry server and from 
other clients latched onto the same mailboxes. I suspect that one 
reason some systems limit concurrent sessions  is that they don't 
have (or haven't be configured to use) efficient filesystem event 
monitoring, and the alternatives are quite burdensome. In the case of 
Courier, it looks like it still relies on SGI's FAM, an abandoned 
project that doesn't really work well anywhere but Irix and Linux. 
Dovecot has avoided that at the cost of having to understand each 
system's unique approach to that issue.




-- 
Bill Cole
bill at scconsult.com