I would like to register my custom protocol with Y! Messenger.
Please see the image below. Y! Messenger understands mailto:
, ymsgr:
, but not my custom protocol myapp:
. The custom protocol is registered on both the machine sending the IM, and that receiving.
My guess is that you wish the Windows Rich Edit control to autodetect these links. But then I am afraid that this cannot be done, for according to the official documentation, Rich Edits do only autodetect URL using the predefined protocols.