Comment 29 for bug 584529

Created attachment 499762
nsSocketTransport:5,nsHostResolver:5 log

Another log adding nsHostResolver:5. The behaviour was a little bit different this time in that it actually updated the mailbox before I got a chance to hit "Get Mail" a second time. First time, though, I got the error message as usual.
AFAICT it confirms that nsHostResolver is indeed caching the initial lookup failure (timestamp 2010-12-26 15:54:33.688102).
It appears that nsHostResolver treats any lookup failure as NS_ERROR_UNKNOWN_HOST which is perhaps a bit too naive. Ideally, it would distinguish between a communication failure and an actual NXDOMAIN condition, and avoid caching the former, or at least use a much shorter cache timeout.