Utility to flood Contact list in Thunderbird E-Mail client to rich/plain text preferred format

The largest complaint I've heard from people switching to Thunderbird from another E-mail client (and one I've had myself) is that during the address book import process, the contact's preferred message format is set to "Unknown", which means when you compose mail to this user, no matter what your global setting is, it will always send plain text. This is a bummer if you've spent a lot of time formatting the e-mail to include header sections and other richtext content. Finally it bugged me enough that I did something about it.

This is a free utility to flood all contacts to either allow HTML mail or plain text only. It's not quite automatic because I didn't want to take the time to learn the Mozilla address book file format, but all you have to do is export your address book to a common format (LDIF), delete all the address in your book, run my program, then re-import the files. My program renames the LDIF file to place a ".orig" extension on it, so if there are any problems, you can always re-import directly from that original backup.

Screenshot:
Program exec (sorry, no installer!): Download
Program source code (Visual C# 2008 Express Edition Solution): Download