This page will explain how to create a
.xml file that you can place in the
$INSTALLFOLDER/default/isp to do a variety of things. This page applies to Thunderbird (Mail/News).
These files allow for adding to the New Account wizard a new option, and help with, among other things, deployment of custom Thunderbird.
The files are simple text files, in UTF-8 encoding, so use your favorite modern text editor. A working install of Thunderbird is also handy for testing.