Any emails in Inbox which you think are 'Spam': If you manually select 'Mark > as Spam', then your 'Account Settings' > 'Spam Settings' should be set up to move them to the 'Spam' folder. You should set up Spam Controls to auto put emails in the Spam folder. if you need more info on this - ask - and I'll eleborate in another comment. If this is an Imap account then the server will also be putting emails that it thinks are spam into the Spam folder. In Spam folder : If the Spam flame icon is red/orange then Thunderbird put it in Spam If the Spam flame icon is grey then the server put it in Spam. You do not delete the emails in the Spam folder, you just right click on Spam folder and select 'Empty Spam'. Those emails never go to trash. They are just completely removed. 'Trash' sometimes called 'Deleted Items' or 'Bin' (it varies depending upon the server). Trash folder is for unwanted general emails. When you delete emails they should be set up to go to 'Trash'. That means if you delete in error, you have a chance to recover the email back to eg: Inbox. Many servers now have the policy to auto remove/delete emails from the server Trash folder. Some servers do it after emails have been in trash for 30 days, others do it after 7 days, so it can vary from server to server. I would need to know what server we are talking about in order to see if I can find out what their policy is on emptying TRash. This effects Imap accounts because imap folders synchronise with server folders. Imap accounts can only display whatever is on the server. That means you do not have to empty the Trash. Although nothing is stopping you from doing it yourself. Either manually - right click on Trash folder and select 'Empty Trash'. Or set up the 'Account Settings' > 'Server Settings' to 'Empty Deleted Folder on Exit'. If you have an Imap account that means those emails have been deleted off the server. Many servers do offer a means of recovering some emails, but not all. I would need to know what server you are using. Gmail ? Yahoo ? BT? Outlook ? etc Recovery is done directly via the webmail account accessed via a browser. AS an example - if you use the Yahoo server then read this: https://help.yahoo.com/kb/recover-lost-deleted-emails-sln2552.html Gmail can try to recover anything deleted in the last 30 days. useful Youtube video: https://www.youtube.com/watch?v=x1892EtHpIU