I may not be understanding something here, because it looks to me that the answer to your question is in the screenshots you posted and that you appear to have already noticed, which is that spurious 127.0.0-1.1 IMAP folder showing the contents of what appears to have been a Gmail account including an All Mail folder taking up about 38 GB of disk space all by itself, and which doesn't seem to correspond to any of the mail accounts you currently have in Thunderbird, hence Thunderbird not showing that…

The 127.0.0-1.1 IMAP folder is my current Protonmail account. TB shows the All Mail folder for the Protonmail account as 5.9 GB but as you note the size on disk is 38 GB. How do I get this down close to the value shown in TB?

The 127.0.0-1.1 IMAP folder is my current Protonmail account. TB shows the All Mail folder for the Protonmail account as 5.9 GB but as you note the size on disk is 38 GB. How do I get this down close to the value shown in TB?

The Folder Pane size of 'All Mail' is a total count of whatever emails you have in the 'All Mail' list of emails. The profile size on disk is the real size it is currently using. When you delete emails they get 'marked as deleted' and hidden. So, this profile 'All Mail' mbox tells me you have a lot of 'marked as deleted' emails because you have not been compacting that folder.

As that 'All Mail' mbox file is now huge, it could be difficult to compact. Compacting means that file needs to be opened and then scanned for all the good wanted emails that are not 'marked as deleted' and they get written to a new 'All Mail' mbox file. The original is then deleted and replaced by the new mbox file. However, that single text file is very large and could cause an issue when trying to open in order to compact. And if that file has any corruption it could lose emails and that would be disasterous for you because that server stores everything in the 'All Mail' folder.

So normally I would suggest compacting the 'All Mail' folder, but in your case, I would advise against this and because this involves the 'All Mail' folder and it's too risky.

I would strongly advise you do the following in order to fix this issue. In Folder Pane.

• Right click on the name of the account folder and select 'Subscribe'
• Select the 'All Mail' folder
• click on 'Unsubscribe'
• Click on 'OK'

This should remove the 'All Mail' folder from the list in Folder Pane. It should also remove the 'All Mail' mbox file as well from the profile. Then Exit Thunderbird and this will update all the necessary files in the profile.

After a few moments allowing background processes to complete - Start Thunderbird. IF you want to see the 'All MAil' folder again In Folder Pane.

• Right click on the name of the account folder and select 'Subscribe'
• Click on 'Refresh'
• Select the 'All Mail' folder in list
• click on 'Subscribe'
• Click on 'OK'

Allow it a bit of time to synchronise with server and get all those emails downloaded again. Now you see a bit difference in the profile 'All Mail' mbox file.

Is there any reason why you have subscribed to see the 'All Mail' folder ? It is just a complete copy of everything you already see in all the other folders.

I generally advise against subscribing to the 'All Mail' folder because if something goes wrong eg: Anti-Virus decides it does not like something in that file you could end up losing emails. The imap folders should not be regarded as independent from the server because all imap folders synchronise with server to match whatever is on server. Anything deleted in imap is also deleted off server. It would be catestrophic for you if anything on your computer corrupted or quarrantined or deleted that 'All Mail' mbox file.

Basically - it's using a gmail format where all emails are actually stored in the 'All Mail' server folder, but they realise this is not of any use because there is no means of knowing whether those emails are incoming or sent or archived etc. Hence why the server (as seen via webmail) applies labels which work like a tag to create a virtual copy in eg: server Inbox. Thunderbird nor any email client knows about labels, they download whatever is in Inbox and it gets displayed in imap, but that downloaded copy is a separately stored email. Hence if you see Inbox and All Mail you end up using twice the amount of space to store emails. But if you delete an email in Inbox then server will auto delete from 'All Mail' meaning that 'All Mail' folder is being updated constantly as seen in Folder Pane. Same when you move an email from Inbox to Contracts - that just forced the server to alter the 'label' in the 'All Mail' folder.

At the end of the day it's up to you.