[Dovecot] Dovecot upgrades break Blackberry instant email (BIS)

[interfaSys sàrl]

 Hello,
Just like when upgrading to 1.2, upgrading to 2.0.1 confuses RIM's BIS
servers and users don't have instant email anymore on their Blackberrys.
Under normal conditions, the BIS servers keep one open connection per
email account with Dovecot.
They're using IMAP IDLE to monitor changes and push them to devices very
quickly.

After an upgrade, all changes.
The BIS servers can't maintain an idling connection anymore, they just
poll the Dovecot server when they feel like it (every 2-15 minutes).
There is one way to fix this on the devices: The users have to re-create
the email account.

I don't find this very convenient and was wondering if there was
something that could be done on the Dovecot side?

Last time it happened, I tried clearing the indexes and resetting file
permissions, but nothing helped.

Cheers,

Olivier