This is definitely already a solved problem - for open or homogeneous platforms. This is why it's still an issue for everyone else... Microsoft's general attitu

This is definitely already a solved problem - for open or homogeneous platforms. This is why it's still an issue for everyone else... Microsoft's general attitude is, "everyone should use Outlook", Apple wants you to use Mail, Google wants everyone on Gmail, etc. I'm sure this is rarely an issue inside those companies - threading "just works" since coworkers all use the same clients. So not only do they have zero financial reason to support interop or openness, they probably don't even know its an issue.