Hi, welcome and thank you for your question. My name is ***** ***** I am glad to assist you today.
I am very sorry about your issues. Are you using Windows XP, Vista, 7, 8 or 10?
Also, in your Thunderbird, have you tried to empty your Trash folder? If not yet, please give it a try - empty your Trash folder and then test deleting emails again.
Please let me know so that I can help you further. Rating is only required when we are finished and when you are satisfied with my service.