Until yesterday all was fine. Yesterday I was informed that the certificate from my email provider "VirginMedia.com" was not trusted because it hasn't been verified by a trusted authority using a secure signature. I ignored this warning message once and sent out an email as usual. A little while later I received an email from a manifestly false address: it was claiming to be from myself, but from a domain that I did not recognise. I then changed the location of my profile directory (with all my stored emails) and uninstalled Thunderbird. When I reinstalled Thunderbird, I was told that my profile was not accessible, and Thuderbird exited without giving me the option of creating a new profile. I was very surprised at this. As I had uninstalled Thunderbird and changed the location of my profile directory, I had expected Thunderbird to take me through the initial set-up process, but it did not do so. When I put my old profile directory back where Thunderbird expected it to ne, namely: C:/Users/Stephen/AppData/Roaming/Thunderbird/Profile/k9khp55z.default/Mail my original problem returned. I do not know whether this is a problem with Thunderbird or with VirginMedia.