Hi, I dual boot Debian 11 and Windows 10 and have Thunderbird installed in each. I have never had problems with email discrepancies between the two installs. But today I performed a major prune operation on the Debian installation, I deleted lots of mails and attachments that were taking up space. Sometimes I deleted the entire email, sometimes I kept the email but deleted the attachments from within the email-reading window. I did this both in inbox and sent. You can see this account (underlined in red to the left in the image below). After the pruning/compacting the inbox was 326MB (down from 1.1 GB). I then booting Windows 10 and started Thunderbird whereupon syncing occurred to reflect my pruning. At this stage the number of emails in inbox and sent were the same in both Debian and Windows. But when, after emptying trash and compacting folders in the Windows install, I go to wonder at all the saved hard drive space in Windows I notice that the account's corresponding folder seems the be two folders+subfolders instead of one (red underline). There are two inboxes, two sent, two of everything. One inbox file (green underline) matches exactly in size the size of the inbox on Debian, but the other one (green dotted) in hugely inflated. And searching the two inbox files (green underline/dotted) in the Windows install at random for emails '''still existing after the prune in my Debian inbox''' they show up in both of the Windows inbox files. I see the same thing for another two accounts as well. What is going on here? /Peter EDIT: adding image from windows install showing the size of the inbox in question from within TB. Corresponds with Debian size but raises questions about what the green dotted inbox actually is.