If you have problems with your program, make sure that you download and install the latest version available. You can obtain a download link for the latest version from its review page on Software Informer. This way you can overcome some errors that were present in earlier versions. The latest version of Thunderbird was tested, and no matter how many address books were exported, there was only 1 resulted file. It seems that this is how the program was designed to work, and this can't be changed. Moreover, the resulted file isn't automatically open. To view it, you need to navigate to the location where this was saved.