It sometimes happens that I delete a mail by accident because it does look like spam or a message that I do not longer need. Thunderbird does not display that message anymore if it is completely deleted from the mail client. Unknown to many Thunderbird does not delete the messages but flags them only which means it is relatively easy to recover corrupted or deleted mails. This method only works if you have not compressed the mail folders because compressing removes deleted messages from the mail files.
