All my mail from before Sept. 1st has had its contents deleted.
I went into my Thunderbird mail tonight to download today's mail. I went through some of my mail still in my inbox folder so that I could answer some of the mail (some mail has been in there for a while, as I have active items going on). I noticed that the content of all my mail from before Sept. 1, 2016 has been deleted. When I click on the email from any of those dates, there is no content. The 'from', 'to', and 'subject' show up but no content.
I had a similar problem in March of this month, when I returned home after a trip to NJ, ALL my mail before a certain date had been deleted.
I have about 470 emails in my Inbox. There have been times I've had over 1000, and never had any problems.
Wšykne wótegrona (1)
I have over 20,000 emails in my inbox going back years. What I think you will find in somewhere in your anti virus product a proud announcement that they found a virus or threat and automatically fixed it. By deleting all your mail up until that time. But they will not mention the destructive nature of the fix.