A big thank you in advance to all who take the time to read this, especially those who feedback. Firstly, some quick details about my environment: * Windows 11 Pro (fully patched). * Proton Mail account – 2 proton address, and 10 addresses across 3 custom domains. * Thunderbird 146.0.1 (64-bit). * Proton Mail app 1.11.0 (5.0.324.1). * Proton Mail Bridge 3.21.2 (br-215). This has been intentionally set to “Split addresses” mode, where (according to Proton) I can “Setup multiple email addresses individually”, and I have also disabled “Show all mail”. * I have set up a new Thunderbird account for each Proton Mail address. After only a couple of days of migrating my Outlook messages over to Thunderbird (in Proton Mail), two items of concern became apparent – this query here is the much more important issue; I’ll raise another question here on the community for the other problem. Now I understand that all of the folders imported or created in Proton Mail have no association with mail addresses. I also expect – but please tell me if I’m wrong – that on the basis of Thunderbird being configured to “Subscribe” to all folders, as well as having the server setting of “Show only subscribed folders” ''unchecked'' for each account, then I should see all messages in all folders across all accounts. I’ve only just started the migration, but even now I’ve imported ~7,000 messages and – based upon the presumption that all accounts ''should'' see all folders and their messages – it appears to be a very inconsistent (and worrying!) picture (see attachment). So far, I’ve: * Resynced the Proton Mail Bridge. And resynced it again. And again! * I’ve even run a repair on the Proton Mail Bridge. * Before any of the two steps above began, I deleted the accounts and data from Thunderbird. When Proton Mail Bridge has then finally resynced, I added the accounts back in again. * I’ve even gone as far as deleting my Thunderbird profile to effectively start it all again. And finally, on a second machine (Dell laptop, same config as desktop above), I installed the same three apps and then added only ''one'' account to Thunderbird, which returned me just the one single message in the Inbox - absolutely nothing in any of the folders. The Proton Mail app does show all messages in all of the correct folders, so could this be a Thunderbird issue, a Proton Mail Bridge issue, a combination, or something completely different. As I said at the beginning, any and all constructive and helpful feedback will be most gratefully received.