Unfortunately I cannot say WHEN this started (within the last year?). I'm using Windows 10 and Thunderbird 115.5.1 When I have a message that I know I never care to see again, I press SHIFT+DEL to get rid of it immediately and bypass putting it in the Trash. I have ALWAYS done this. Something has changed semi-recently though, and at first I thought I was just mis-remembering deleting it, but now I have just been suffering with the problem. I use Thunderbird on my personal computer at home using IMAP to connect to my email provider. I use my email providers web based email interface when I access my personal email from my work computer. Both Thunderbird and the email providers web based email interface access the same email account. At home, using Thunderbird, if I SHIFT+DEL messages they are removed from my Inbox (and NOT put in Trash). Later when I go in to work and login to the web based email interface, the messages are still in my Inbox. While at home using Thunderbird, _IF_ I remember to "compact" my Inbox, then later when logging into web interface of email, the messages are NOT there. I have not changed any settings in Thunderbird. This is just some semi-new issue. As I said, I have always used SHIFT+DEL to get rid of messages. My Thunderbird mail settings are set to "When I delete a message move it to 'Trash on [my imap server]". And this DOES work. If I just press the DEL key to delete a message, it gets removed from the Inbox and moved to Trash. And then if I login to the web based mail interface, the message is no longer in my Inbox (and properly in the Trash). So there seems to be some kind of disconnect with the "Immediate Delete" (SHIFT+DEL) option. Is there some setting where I don't have to remember to "compact" my Inbox? I have "Compact all folders when it will save over 200MB in total" enabled (I have not changed this setting). That is about the only setting I can find about compacting, but I'm not sure it's really a "compact" problem. Also of note, is that I RARELY QUIT Thunderbird or turn off my computer (I usually put it to sleep). But again, this is nothing new. And QUITTING Thunderbird does not help anyway. SHIFT+DEL a message, QUIT Thunderbird and then check email via web based interface, and the message is still there. I DO NOT (and have NEVER) had the option (under my account settings) "Message Storage -- Clean up ("Expunge") Inbox on Exit" enabled. Right now, the only "fix" seems to be to remember to compact the Inbox. :-/