If you are using sort by Threaded and the Threads are in a collapsed state: If you select the top level collapsed state thread email and click on Delete or use Right click and click on the Delete bin icon, you will get a pop up messages which says "This will delete messages in collapsed threads. Are you sure you want to continue?" If you click on 'Delete' button - it will delete all threads in that collapsed thread. If you delete any single email not in a thread then email follows the instruction set up in account settings for the account. eg: Move it to the TRash You do not get a warning when only deleting a single email and it is going to a designated folder. '''If you use the 'Shift' + 'Del' key''' This will pop up a message that says: " This will delete messages immediately, without saving a copy to Deleted. Are you sure you want to continue? " If you click on 'Delete' button - it will delete the email and by pass the Trash. There is no Undo option. This is very use if you use a Gmail imap account and have same email stored in various folders but you only want to remove a label not delete actual email from the 'All Mail' store, so it means any other copies with labels for other folders will still be visible. '''If you want to Empty the Deleted/Trash folder''' Right click on Trash folder and select 'Empty Deleted' You will see a prompt: "Delete all messages and subfolders in the Deleted folder?" Click on 'YES' and it removes all emails and subfolders that exist in the 'Trash'. If you do not use that 'Empty Deleted' option but instead select an email that is already in the TRash then you should get a prompt: "This will permantely delete messages from Deleted. Are you sure you want to continue?" Clicking on 'Delete' - just deletes that particular email from the Trash. IF you select several separate emails that are not threaded they will display as X conversation in the Message Pane When you click on 'Delete' button - it means they all get move to TRash or as per Account Settings. There is no warning but the Undo Delete is an option. There are several different warnings and it also depends upon what you have selected. I suggest you attempt to delete an email from Inbox in order to invoke that pop up message - then get a screenshot which shows: you have selected the 'Inbox' folder You have selected one single email in list The warning pop up message Obviously do not click on the Delete. Upload that image file to this forum question.