Filters only work for a few messages
I have many filters set up in Thunderbird, and they're great when they work, but I cannot run (at least some of them) on entire folders or "large" numbers of messages. I'm not sure what the limit is, but it'll do a few hundred and not a few thousand. If I select a message or a few dozen, it works. If I select, say, 2000 messages, and tell it to run filters on selected messages, it just doesn't do it, or starts to do it (shows the progress indicator) but stops before it's done and doesn't move anything. Additionally, once I exceed this limit, filters don't seem to work at all until I restart Thunderbird.
The main filter I know of that has this problem (which has been a great problem for me) is one to move old mail from one box to a local folder. It selects on addressee and age in days. It works fine if I do a message or two, or in very small batches, but not en masse. If there's one thing computers are good at, it's en masse, so this is frustrating.
Alle antwurden (3)
Mail servers aren't made for mass transactions. So I'd rather suspect the problem on the server than with Thunderbird. Presumably you'd see the same behavior if you'd do the mass move transaction manually, without any filter involvement.
You're right- I'd forgotten I'd tried that (this is an old problem causing me new pain). It's the moving (specifically the downloading, it seems) that's the problem.
I'll reiterate though, why can't Thunderbird insulate me from this problem by doing whatever it has to move mail en masse? I don't care how long it takes or if it has to do them internally in very small batches. I can do it in small batches from the GUI, so it could do it too.
Making me, a human, do things over and over instead of software doing it is madness- that's what we invented computers for- and the point of a user-level application like Thunderbird is to protect users from technical details.
Feel free to raise an enhancement bug. https://bugzilla.mozilla.org/