Virtually all HTML content crashes CM. I do not even have to view it. Just going to a folder with the top email containing HTML causes crash. I have unintalled and reinstalled. How can I do a completely clean uninstall, and then try a reinstall? Help, please.
After uninstall, just make sure "Program Files (x86)\GNU\Claws Mail" folder does not exist. Registry entries should be cleaned up properly by the uninstall process, but if you like, you can do a regedit search for "claws". User data (accounts, preferences, etc.) are in your user folder, in "AppData\Roaming\Claws-mail", if I recall correctly.
I think this is fixed in 3.12.0-1. Fancy plugin is much more stable. Feel free to reopen if you have particular messages which make Fancy crash.