No Stupid Questions

Yes and its very easy actually.

1. Create a folder on your computer to save the files to. Like "email-archive" or something.
2. Open Thunderbird
3. Select the emails you want to save (If you want to save an entire folder, like the Inbox folder for example, just open that folder and press Ctrl + A to select all emails in that folder)
4. Right click anywhere in the list of selected emails
5. Click "Save As..."
6. Select the previously created folder in the save dialogue
7. Done. You now have thousands of .eml files :)

They are just specially formatted text files that can be opened with email programs or text editors. This means you can easily do a full file content text search through the entire folder if you need to find something.

Yes you can, but the exact process is lost on me as I haven’t used Thunderbird in ages. It should be able to export your mailboxes into a standard format (is it mbox?) or if it’s only a few specific emails you should be able to export them individually as .eml files.

In Outlook it’s called the .pst file.

In thunderbird I think it’s an mbox file.

Not a lot of mail apps out there. I’d go with thunderbird mbox.

Yes, you can, you have a user profile in Thunderbird, that is where your emails are stored locally.

You should first look up downloading your emails locally, this depends on the connection to the mail server.

If you are running POP3, it normally downloads your emails directly to your computer automatically, if you are using IMAP, then it normally doesn't.

Thunderbird is a popular email client, there are plenty of guides...

I did that once as part of an escape from Google. Just downloaded everything to thunderbird and then severed the link. Then thunderbird became my source of truth for emails. Whatever I needed to delete, I did (subscriptions, ham emails, et) and then I uploaded to another vendor which was much cheaper for the starting tier. I can skip that last step.

Just make sure to severe the link so thunderbird doesn’t do anything stupid. But you can also take a backup of your inbox in case thunderbird does do something silly.

Once you've downloaded all your emails, if you go to Tools > Export, you can back up your entire profile there.

I'd recommend you set up archiving first (I have it archive to year then year-month, but what works for you may differ), then Ctrl+A to select all your messages and click the Archive button. This'll make the archive a bit more manageable.

Then you simply take the backup to another machine and do Tools > Import. All your messages will be imported, and you'll have a well-organised history complete with full-text search on both machines. :)