No sooner did I submit my question, than I went back to my mail and checked if I possibly had some filter on it.

I selected the the mail icon for "show only unread messages," and now all my mail shows again.

I have never, ever used that icon before. I do often filter messages by looking for certain words in the subject, recipient, etc.

This outcome is good but totally mysterious to me. It would be great if anyone could offer some insights!

Thanks again!

~Ellen

I was just about to say check for any filters that may be applied.

In image, you have two filters selected. 1. On the right side - that filter is 'Show only messages from people in your address book' 2. On far left side - that 'pin' filter means apply keep any selected filter applied when selecting another folder.

It's all too easy to select a filter. You are not the first to wonder how it occured. The 'show only unread' messages is right next to the X for clearing the search data and if searching you may find the 'Body' filter option is directly below. It really depends upon how wide you have the window.

If you had used 'Tab' and inadvertantly tabbed onto that filter or perhaps you had the mouse pointer over it and walked away, screen had just gone into a screen saver mode and you clicked on eg: Spacebar to revive etc. I've also known cats to be excellent keyboard users! I had to help someone recover a load of emails because cat had managed to select 'Shift + A' and then press 'Del' as it wandered across in front of user. Fortunately, in this case, panic was averted and normal service resumed.

Thanks very much, Todd.

Everything you wrote makes sense, except . . .

Even if I inadvertently selected a one of the filter icons on one email account, it doesn't make sense to me that I would've done the same thing on all three accounts. (No cat in this house.)

Is it possible Thunderbird did something on its own? As a user for more than a decade, I'm really mystified!

Glad to be out of panic mode, but looking forward to being in "aha" mode, Ellen