I suggest you rethink your approach, leaving all messages and folders on the server and then running a manual filter as needed to download the desired folders to PC.

My current email archive is reaching 50Gb so leaving them on some third party server is not practical. In addition leaving too much in on-line visible folders does slow down the mobile devices. Today I AM leaving new messages on the server and while I can't see the history once they are moved to local folders it is working for me. The problem is that 'running a manual filter' from my current list of 50+ is time consuming when a simple 'run all filters' would do the job. I could also make a case for a toggle to switch all those filters from manual to auto which would actually be better for the 95% of the time I am at home. It is only the small amount of time away when I may need to see urgent messages which will later be archived to the relevant local folder.

Of cause a sync function to copy those local folders to the phone and tablet's copies of thunderbird might be another solution, but in an emergency I can see the desktop machine remotely to look historic stuff up ;)

OK I think I may have worked out what david is saying but still need to work out the fine detail. Move the library of email filters to the local account and enable them all so they are actioned when I move stuff TO the local inbox? Will that work? Have cloned the email filters to the local folder account, but still have to manually select one for it to work :( In some ways it's tidier anyway as it's processing messages I've already decided are for filling and all the dross is killed on the incoming accounts ... but it would still benefit from 'Run All' ...

It's still puzzling, as I do not see why you want some messages on PC at all. Your archive is online, so why not leave them with the others? When you are not at home, do you need the 50G of archive with you? Or just the recent messages?

My ARCHIVE is on the network here and I only have a 1Gb space on the internet facing email server provided by my domain registrar. Any more capacity there would cost and I don't need it! I don't access old stuff as often as I used to, but being able to see traffic back to 1995 has been useful in the past, so today I'm just tidying current messages and saving them to a tree of folders so each client, project, supplier and the like is separately filed away and I can go to a folder and see that traffic sometimes 30 years worth. Everything is backed up to the servers here and I am not reliant on some third party at all. Today all I see on the mobile devices is the current traffic such as the email about your post ... which will get suitably filed even though some will say 'just delete it' which was the mantra at one time? That thunderbird can handle my archive is nice even if it was touch and go at one stage ...