When I installed RoundCube as a Sandstorm app, it wasn't clear to me at first why I couldn't receive mail, even though I'd set up email in the admin panel. The answer was that I hadn't yet read up on how to set up the server for incoming mail:
I'm not sure if this is Sandstorm's responsibility (it probably knows that RoundCube is asking for this permission) or RoundCube's (since it's what even non-admin users will interact with directly) but I wanted to at least toss this your way as a first pass.
When I installed RoundCube as a Sandstorm app, it wasn't clear to me at first why I couldn't receive mail, even though I'd set up email in the admin panel. The answer was that I hadn't yet read up on how to set up the server for incoming mail:
https://docs.sandstorm.io/en/latest/administering/email/
I'm not sure if this is Sandstorm's responsibility (it probably knows that RoundCube is asking for this permission) or RoundCube's (since it's what even non-admin users will interact with directly) but I wanted to at least toss this your way as a first pass.