I've been using Gmail for quite a while and I have about 15000 emails in total, only partially sorted using labels. Using Gmail itself to sort them is a nightmare for me, so I decided to use Thunderbird instead. My plan was to download the emails (IMAP, not POP3) and move them to a local folder to store them and have them removed from Gmail. I assumed the emails disappear from Gmail if I move them to a local folder, but that seems to be only true if you move the email from the Inbox, and not "All Mail".
Here is my problem: I had the emails in Gmail sorted using labels. I removed all those labels from the conversations and I expected all my emails would land back in my inbox, but they didn't. They are all visible under "All Mail" from what I saw, but they're not in the Inbox. The Inbox has a fraction of the amount of emails that "All Mail" has.
Where did the emails go? All I want is to move all my emails to a local folder on Thunderbird and have them removed from Gmail automatically, but I can't do that, because the "All Mail" folder/label seems to be a copy of all the emails, so if I move those, the emails are still in Gmail.