To follow up, I clicked Offline in step 4 and it prompted me as to if I wanted to download mail before going offline - I said Yes. I waited (hours) until that status showed offline. I then began copying the IMAP folders from the Thunderbird account to Local Folders. It's quite evident that it didn't succeed in downloading all the mail because I got several messages like the attached - complaining it can't copy messages that haven't been downloaded.

Once the copying seems to have finished, I guess I'll have to go back Online, click on each of the missing folders and then copy them to Local Folders.

Suffice to say my confidence is not high that I'll actually have all the emails from gmail in my Local Folders when this is done :-/

pi

Refining the problem.. I was zoomed in too far. I think the actual question is:

How do I download all the IMAP folders, headers, messages and attachments from my gmail account into a Thunderbird account *and* how do I know when it's done?

I've done all the things I can find for this process but I have absolutely no certainty that it's complete or that it worked.

For part 2:

Note the quantity of messages in each folder on the server before you start?

And know that the process is done when the same quantity of messages is in each folder in Thunderbird?

For part 1: subscribe to only one new folder at a time?

Thanks, @Scooter.

Your ideas are good, it's just that brute force is going to take a very long time and a lot of manual effort. I have probably 100 folders nested into trees and almost 80,000 messages. To subscribe to one folder at a time I'd have to remove my thunderbird account and start over.

I'm probably about to get banned on the gmail side from the high IMAP activity. I'm already on my third full download attempt in as many days ;-) Given that, I might just be best at this point to compare # messages per folder as you suggested: gmail web vs gmail account in thunderbird vs Local Folders in thunderbird.

My point is still that I shouldn't have to do this much manual work to get the end result. It should in theory "just work". That is obviously not the case as evidenced by my error messages above. Gmail shares responsibility for that with its enslaught of (possibly non-standard) errors, throttling and daily limits.

You can subscribe to one folder at a time, and probably avoid problems that arise from synchronizing many large folders at once, without needing a new profile. Do you know how to subscribe and unsubscribe in Thunderbird?

Yes, I know how to subscribe individual folders. I started looking at counts yesterday and the difference between gmail web and gmail account in thunderbird are in the hundreds per folder.

I'll try subscribing one folder at a time and see if that corrects the counts. Thanks.

I'm going to focus on gmail label folders first since the counts for the default folders are out. For example, gmail web Inbox says 38,092 messages where thunderbird gmail account Inbox says 52,456 messages! Yes, I have "Don't override filters" option On under Inbox > Filtered mail in and General > "Smart features and personalisation" turned Off in Gmail's settings.

I do not know anything about gmail. If you have specific problems in that part of your project, you may want to start a new thread here.

If you leave Thunderbird online, and you have global search enabled, then I think if you look at the activity manager you can see whether any message are syncing or being indexed. When you reach a point where there is no such activity then you could go offline and do your business. But, there is still no absolute guarantee everything is downloaded. And I know of no tool that can tell you whether all messages or fully downloaded.

Why don't you use https://accounts.google.com/ServiceLogin?service=backup ? I've never used it, but It seems to me that might be more efficient.

Another approach, install https://addons.thunderbird.net/en-us/thunderbird/addon/glodaquilla-ng-index-ondisk/. There is a column g_Offlline which, if you are programatically skilled, you might be able to query its value on each message for various folders.

Hi Wayne, Google Takeout may be the least painful way to do this. I didn't see your answer before I marked the question solved. The only problem with the mbox it creates is that every thing is in the one folder instead of the many labels I had setup. In the end that might be an acceptable compromise - I at least know I have all the messages without having to make heroic efforts and if I need certain emails then I can just search the mbox archive for them.

For those who go the Google Takeout route: https://www.howtogeek.com/709718/how-to-open-an-mbox-file-in-mozilla-thunderbird/

Thanks, pi

P.S. This is really the best solution since it ensures all the messages are downloaded and attached to Thunderbird as an archive without heroic validation efforts.