1. [x] Unit tests seem to break due to `mu4e-mu-version` being a void variable. Not sure how this can be fixed. mu4e needs to be loaded to know its version. We could of course cheat with something like ``` elisp (if (and (boundp mu4e-mu-version) (version< mu4e-mu-version "1.10")) ... ``` But this feels like not a proper solution. Maybe something with `eval-after-load` or something like that? 2. [x] I What about users of 1.9, which started the transition to the new interface? In my opinion that's officially not a stable version but a development-version, so I wouldn't load any backwards-compatibility code for that. As a non-stable release, people who used that are likely to be users of bleeding-edge mu4e versions and will update soon. 3. [x] I would add a comment above that `if` explaining why this is being done