Email arrives, is either read or not read and only seen as header, I go back to Thunderbird and it is no longer visible. The message count is 46, yet when I count them physically, there are only 43 showing, so there are three more but not showing. If I go to find, they show in the results page, but when I click on show as list, there is nothing in the list and the result has disappeared again. The messages in question still show on both my husbands and my phone, we have not used the phone to either read move or delete them at that point. I have tried the thing with threads, but no avail. There is nothing quaranteened in Windows Defender I have tried to follow instructions in another answer regarding X Mozzilla Status, but fell at the first hurdle: Help>Troubleshooting Information, click on show folder = there is nothing there that allows me to click on show folder, I have checked all over that page and all drop down menus. This is not the first time this has happend, last time we just gave up, forwarded the message in question to a gmail account and worked from there, but this is just so infuriating, HELP please...  :-(