Alternately, I wonder if I could just put the Thunderbird folder that includes the user's profile into a cloud-synced folder, so that the data would be housed in the cloud but could be accessed via the Thunderbird app locally.

A couple of thoughts: - look for any files ending in NSTMP - those are created if a compaction fails and can be deleted - look also for duplicates, such as inbox-1, etc. When you see a dash and number, a duplication was created and thunderbird isn't using older account versions. If you see that, the duplicates can be deleted, but you would first need to look at the account 'server settings' pane to verify which folder was being accessed. - if the person uses the AllMail folder, which is a full duplicate of everything, I encourage people to unsubscribe from it, since it serves no real purpose on the PC. Whatever messages are there are also in other folders. - if you have server available, the account can be offloaded there and still work fine, e.g., drive E or G. The location is set at the account's 'server setting' pane. - for backup, thunderbird uses a profile with accounts and settings. backup the full profile when Thunderbird is not running for best results. The profile folder is the one that includes the Imapmail folder

I am NOT the superguru here, and others may offer better suggestions. but what i mention does work.

Thanks David. It's a MacBook, not Windows machine, so although we don't have an onsite server, we do have Google Drive folders which are linked to the account and could function as the server.

So my workflow would be: 1. Backup the current /Thunderbird folder to Google Drive 2. Use the server settings pane to designate the Google Drive folder as the account folder location

Sound right? I'll give some of those other options you mentioned as well a try.

Yes, here are details as I would do that - exit TB - copy the account folder from imapmail folder to the other drive - start TB and change the link to point as desired and verify - exit TB and delete the original message folder

I may have more suggestions if you did a screenshot of the view of the folder from OS file manager, the view that lists folders and sizes.

Attached is a screenshot of the imap.googlemail.com folder. You can see that the mail issues are the All Mail file and the Sent Mail file, which together add up to almost 40GB.

I've also been looking at [this help article] which suggests that I create a new profile rather doing it through Server Settings, any thoughts on that? It's under the "restoring to a different location" header.

On the screenshot, the important and starred folders are also gmail folders, not hers. And drafts are not automatically deleted, so she may (if made aware), may voluntarily delete that, as it's almost a gig -- but I respect you would prefer to not require user involvement. If she doesn't use allmail, that's your biggest savings. I regularly encounter users who think it's needed, but it isn't.

Yes, you can move the entire profile instead of the one account. That can be tricky, so be sure that the profiles.ini file is properly adjusted. Thunderbird opens that file first to see where the profile is. If there is an error, it shuts down.

When you say "account folder," which folder are you talking about? I moved the entire Profile folder (I backed up the entire ~/Thunderbird folder to Drive) and then changed the profiles.ini text file on the local version of the Thunderbird folder to access the profile in Drive. That seems to have worked, actually! I've got Tbird open now on the computer and the profile that it's using is the one in the Drive.

But it seems like what you were saying is that I could have kept the profile local on the computer, and just moved the imap.googlemail.com folder to the cloud, then pointed the Google Server Settings to access that folder, and then delete the original.

Do you see any reason why I should do your original method (move Google account folder) vs. what I ended up doing (moving the entire profile folder)? I wonder if there's functionality that I'll miss because the entire Profile is loading from the Cloud...

I was thinking of most individuals, who may update their profile or restore their profile and, if it is not in the default location, sometimes create a horror show trying to put it all back together. Otherwise, I fully concur with moving everything. I regret any confusion there.

No worries. Thanks, you've been quite helpful and it all seems to be working now!

You're welcome. Free beer, all around.