Tutoring said

A group of keys on the keyboard was accidentally pressed. This caused the immediate loss of 2000 emails from my inbox, which I need to have for business purposes. It also made the dropdown icon next to the Write button disappear. The dropdown icon used to give the choice of bringing up blank emails of several of my email addresses and their associated email headers. Now when I press the Write button it brings up a blank email through 1 of my email addresses and the business email header has disappeared. The send button is also greyed out so I cannot send emails. Please assist.

My native Write button has only ever, so far as I can recall, offered options to write a new email message, or set up a new event or a new task. If yours offers something else then you may have previously been using an add-on. I suspect that something like the Stationery add-on may change its behaviour.

Check at Tools|Add-ons|Extensions to see if any add-ons have been disabled.

I'm struggling to imagine what kind of damage has been inflicted on your machine to cause the changes you describe. I suspect your profile is corrupted but I don't know how this could happen nor what keystrokes could do this.

I suppose you don't have a recent backup? Perhaps starting to make regular backups would be wise, particularly if your business depends on email correspondence.

You had 2000 messages in your Inbox? Don't you believe in filing?