With Thunderbird 3.0.1 & Lightning 1.0b2pre (but it's the same with
the old versions of lightning),
I have defined remote calendars that use ftp.
My ftp is limited to 2 concurrents access, so when the synchro is
running, I have the
error 421 You can only have 2 connections SIMULTANEOUS

Is there a way to limit number of simultaneous connections that
thunderbird can initiate ?