I didn’t see in the “about” what jurisdiction (if any) you are incorporated in. I also don’t see if there’s any encryption at rest.
This is important to me because in the US, the government can go to court, get an order demanding a US email provider to put in a backdoor, and then get a gag order so the US company can’t disclose it to users.
And with open-source code, I end up trusting to some extent that the server code matches what is on github, so making it open-source doesn’t stop forced backdoors and gag orders if it’s based in the US.
For someone whose threat model doesn’t include the government (someone not LGBT+, not Latino, not trans, a political moderate with average viewpoints who won’t be impacted regardless of who is in power), it’s not the sort of thing that matters. But for others, it would help to include that information.
It’s probably still a good option for an all-in-one solution for anyone with a very low threat model who wants to get rid of clutter and protect their inbox.