lets see, you want to corrupt anything on a computer, turn it off while it is accessing it's files.

So what your seeing is corrupt files most likely caused by your attempts to stop the legitimate download of your mail.

You also appear to have corrupted your persona address book in the process.

So Help menu > Thoubleshooting information. Select the show folder button Close Thunderbird Delete the file abook.mab in windows explorer (that is your personal address book) Open the folder Mail. Then the att.net folder delete the popstate.dat file (that is the what has been downloaded memory)

locate the file inbox move it to your desktop and delete inbox.msf.

Restart Thunderbird and both your new empty inbox and address book will be created and a mail download should commence (starting with the oldest mail first because that is how it works)

Thank you Matt for your reply. But after getting no responses for a few days I decided to open an ATT email inbox on another computer and downloaded all my emails to the second computer, so that I would at least have them in another safe place. When setting up that account on the second computer, I noticed that the ATT account settings were different to my troubled ATT inbox. So I moved all the remaining ATT folders to my Local Folders and then reset the account settings from server name pop.att.yahoo.com to the new "inbound.att.net". The next day when I clicked on Get Messages, all my emails downloaded to the empty Inbox. And since then the emails are downloading regularly.

But I still do not have a Personal Addressbook. Can you please help me find it and tell me how to restore it.

By the way the original problem was started, as you said, by Thunderbird suddenly downloading all my earliest emails for the second time. Although they were all still in my Inbox on my computer. So I now had doubles. As it seemed to be continuing this I felt the only way to stop this double download was to turn off Thiunderbird. What is an alternative when this happens?