It seems like it is not possible to use mailsystem with features module.
The "SITE-WIDE DEFAULT" and "THEME TO RENDER THE EMAILS" are saved as variables and exportable via features through strongarm... but a New class or New settings is not exportable.
It should be visible if the settings is exportable through Ctools - would this be possible?

Comments

I will be making a 7.x-3.x branch that may suit your needs.

See #1508104: [PATCH] Replace dynamically generated class with delegation

Ok - great. thanks