My ISP was going out of buisness and turned off my service. Argh! I screamed - all my (recent) email is on there! Ok, we'll turn it back on for a couple of hours. Logged in and fetched all my email locally. Phew.
Set up new account on another ISP. Configured my email client. Connected to the new ISP and the email client promptly sync'd my local files with the empty account on the new ISP. ARGGGGGGHHHH!!!!!
On my PC I still have a big directory on the current drive containing files made up from every allocation cluster on the old drive after I imaged it and extracted all the contents, which I go through from time to time. I still have a gap of about a week in my email archive that I haven't found yet.