I can confirm this bug. This has always been the behavior of thunderbird for me, i.e. for all releases ever. It is still present in 1.5.010 in feisty. Also I think this is a duplicate for Ubuntu #51492. The upstream bug number is Bug 278383. No progress for a couple of years.
-- thunderbird: interval checking doesn't work for Unix mail account https://launchpad.net/bugs/89474 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
