The scheme supposes mailto: scheme works (by web browser starting MUA after click to mailto: scheme link). I cannot imagine that is true for majority of people.

The scheme supposes mailto: scheme works (by web browser starting MUA after click to mailto: scheme link). I cannot imagine that is true for majority of people. Perhaps it worked in the past where people used real MUA application, and such MUA is configured as default handled for mailto: in their OS, but today when people mostly use web-based MUA and browser/OS has no idea about it, i would expect it mostly does not work.