I've just installed Thunderbird (for the first time) on a new computer.
I have 2 email accounts - one POP3 and one IMAP. The IMAP one is working
fine. I changed the POP3 one to IMAP as well, but now when I get new
emails, they disppear from my inbox after I've read them.

I've checked the settings etc, but can't see anything wrong. I can't
even see how to changed my email back to POP3 either! It's driving me
nuts and I'm losing all of my emails

Can anyone please help?