Starting from desktop version 4.2.0 and mobile version 5.2.0, offline drafts are now partly supported. You can completely compose a new draft while being offline and click send, it’ll be sent when back online (a notification tells you about that when that’s the case).

“Partly” supported because you would see an offline message if you open Missive while already being offline. You can’t load conversations while offline yet. That being said, even if you don’t see any conversations you can still create new drafts.

Really looking forward to this :)

This is a hint at a larger issue: if you start a draft while connected, then go offline and try to send, the message fails and reverts draft to last synced version, discarding user input :(