If the problem remains, my guess is there is an error in the account setting. I would go to account settings, click the server settings pane and see if the email account is properly defined. It must be the full email address. You might also compare to the setting on the tablet.

I checked the account settings but the problem remains. I can see my incoming emails in AllMail, but not in the Inbox.

Puzzling. How do you have a message that the mailbox does not exist, yet you can read messages there? More information will help. Thank you.

I have the exact same thing. The very fact that it happened at midnight of 10-13-25, and also seeing a flag that that is the very time and date that Windows stopped supporting win10, made me think it is windows issue.

I've spent some time with Protonmail.com, but no solutions. They suggested that I open Thunderbird and check the properties of the "Inbox" folder, then do a repair. This only managed to delete everything in my Inbox. The address showing in the properties box shows "imap://gshantz%40protonmail.com@127.0.0.1/INBOX" The error that comes up when trying to dl new mail, says there is no such folder name. The only exception, is that what's in the properties box show all caps and my actual folder of "Inbox" only had capital "I".

One more confugalty, is that Protonmail requires me to use their Bridge, which stopped allowing win 7 some time ago. So I had to keep using an older update of Bridge to keep using Protonmail. They claim that as long as I continue to use the old version of Bridge without updates, it should work fine. And it has now for some years.

In my searching, I've come across a few notes that Windows had some type of download that allows it to still function past the end of service date. I know this is a lot of extra effort to use Proton Mail Bridge on such an old computer, but I can't afford to upgrade several very expensive programs that won't work past Win 7. But I am very unsure of starting down that road. I just need an answer as to what changed to trigger this crippling dilemma. Appreciate and hints.

I noticed the same - that the problem seemed to start when Microsoft said it had stopped supporting Windows 10. Also, the problem only appears on my desktop (Windows 10), but not on my iPad. However, I don't have access to all my folders on the iPad.

Puzzling. Windows 10 wouldn't stop working just because there is no further support, so my guess is something else, possibly related, is involved. Thunderbird is not sensitive to the differences in 10 vs 11, so I will see if I can locate someone with more insight on problems such as this. I do encourage reviewing your antivirus or VPN (if used) to see there is a tie there.

This is my story-and I am having the same problem though I run windows 11!! But, my problem is limited to getting the inbox - all my other proton folders, and I have many, are accessible. I attached some screenshots.. Hi, Using Thunderbird 140.4.0esr (64-bit). Thunderbird is not able to retrieve my inbox, but it can retrieve any other folders - both ones at top-level and ones inside Folders or Labels. I am attaching screenshots to show Thunderbird activity - I am subscribed to Inbox, and Thunderbird is retrieving messages from the many other folders of my account. Of note is that sometimes Thunderbird appears to address a folder as roy@planalp.net/<folder> and sometimes as rpplanalp@proton.me specifically, rpplanalp@proton.me/INBOX appears to be the addressing of the inbox. My original proton account was rpplanalp, before I connected my domain name.

It has worked fine for a very long time, however, started failing in the last couple weeks and in fact Inbox moved to the bottom of my folders list and I attempted to bring it up to the top. It is notable that I can get the Inbox messages if I subscribe to the All Mail folder, as a poor workaround.