I tried very hard to get it to work, but I simply couldn't get it to connect with my Stalwart instance over JMAP. I do have the permissive CORS and end-points and proxy-protocol seemingly working with my test HTTPS requests, and I also successfully got JMAP to work with the Mailtemi app, but no luck yet with Cypht[0].
Yeah that is kind of issue had me flintch when thinking of using stalwart. As much as it is so nice to install it as a server and ideologies behind it. Looks like gonna just stick with wildduck for now. Just don't like to hedge our email bets on mongodb community edition.