WOW ... if it weren't for my iPhone not listening to whatever the hell thunderbird or tbsync (or both) are doing, it appears I would have lost everything permanently, probably including my entire calendar and contacts list BUT I STILL CANNOT GET THEM BACK INTO THUNDERBIRD ... not even with a fresh install and not importing anything but just deleting the whole thing including the appdata profile folder, and starting from scratch ... somehow, despite the icloud server retaining the information, thunderbird refuses to download it, and is for some reason only fetching inbox and deleted and local folders containing another deleted plus outbox ... and if I try to recreate the same folders, it just does nothing ... this is a seriously bad flaw in the design

... and just when you would think it couldn't get worse, if I create folders locally in thunderbird, I cannot then delete them, when I try to delete them, it gets a server response saying the folder doesn't exist ...

I can create a new folder directly on the icloud server, but tbsync does not sync it, and neither is tb itself ... so it just seems to be completely broken, and doesn't want to be repaired no matter what I do

This is one of the worst design flaws I have ever seen since computers began to be popular in the 80s ... and I have had to now remove thunderbird from all my laptops, so that icloud mail remains only on my phone, and what I hope is that somehow it will rectify itself if the server is perhaps no longer getting requests from thunderbird and tbsync to delete things that the phone says should exist ... because that is my only guess as to what is going on, and I am astounded a bug like this could exist in such an established product

Has anyone seen anything like this before and any ideas how to solve it?

fortunately the icloud server seems to have partially at least reset itself, but full functionality still not returned as yet, and I am waiting a while before trying anything else in case it needs more time to reset all its folders

I can now delete things off the server, perhaps it was busy reorganising when I changed the folder structure to save space ... (?) ... whatever it was, I hope this means the rest of the issue is solved and I will be able to reinstall thunderbird and get my mail running, but I am nervous to try in case it screws it up again ... so if someone from Mozilla and Apple are able to check what is happening with the software or on the server and why thunderbird and tbsync were not syncing, that would be greatly appreciated, because I would like to understand how and why this problem occurred in order to hopefully avoid it in the future ... I am still hoping I can fix this on the desktop applications, but I am giving more time to the server in case it is having to check all its files ... but does tbsync somehow install anything on the server?

HERE IS MY SUSPICION AS TO THE CAUSE - THOUGH THIS IS ONLY A GUESS:

1. A mis-click on the mouse, must have perhaps dragged and dropped a main folder in my iCloud email account in thunderbird, and for some reason, I was not able to see where it had gone, even though there were only less than half a dozen places it could have gone, and it was in none of them ... but nonetheless, it meant all those folders from the parent folder downward were gone
2. Meanwhile, I had already asked the iCloud server to restructure my folders to neaten them up, and with these two conflicting sets of instructions, it was struggling to complete the task while also talking to various mail client applications from my phone to the laptops, all asking for different things, and thus the only one being fulfilled was the phone (an iPhone and therefore more compatible with Apple's methods
3. When trying to reinstall thunderbird, the iCloud mail server was still trying to sort things out, and hence, perhaps I just tried too soon (I have not retried yet, so for all I know, I will still encounter the same problem when I next try again)
4. After a while, the iCloud mail server started to catch up, and so at least now my folders are restructured on the server, and I can once again create and delete folders on the server, and it all matches my phone

SO ... assuming I am at least in the ball park of being correct, my advice to Apple and Mozilla would be as follows:

1. There needs to be better message communication between server and mail client applications to tell each other what is going on
2. The mail server either needs to have a hell of a lot more resources dedicated to completing tasks faster in order to avoid conflicts &/or it needs to LOCK those resources when certain types of requests are made, so that it can resolve the requests before any further sync attempts take place
3. Thunderbird needs to have a lock icon next to the folders in the left hand pane, so that you can lock their positions, and thus not accidentally drag and drop them, but also more flexibility of rearranging everything in the left hand pane when it is unlocked, and better communication with the mail servers to get the mail server to adhere to any valid requests, AND so that the mail client can be organised in that left hand pane in a manner more inline with what the user wants -- eg: it shouldn't matter what order I create accounts in, nor should it matter how they would be organised alphabetically, I should be able to rearrange those accounts to appear in the order I want them, because once they get screwed up, and you have to remove and readd an account, it always goes to the bottom whether you want it there or not, and the "local folder" thing is a bit of a mystery too, without it seems very much control as to where and how it appears in that list