Rather than replacing reliable communication channels such as email and SMS/text messaging, Joinable works in partnership with them, making them even better.
Since Joinable can be used like a group email or text message tool, it's important that it's used responsibly. The app is designed for small, private groups, with an implicit opt-in agreement by the inviter to the invitee that they would like to receive messages from the group. We limit the total number of members that can be included through this "implied opt-in" to 100, which will reduce the risk of Joinable being used inappropriately.
Every email sent on behalf of a group comes with an option in the email footer for a user to change their notification preferences. We'll also occasionally remind members receiving messages through SMS, that they can change how they receive their messages.
It's tricky to get app notifications right for everyone, let alone email and text messages. Finding the right balance of removing friction, reaching everyone, respecting privacy and limiting interruption is impossibly hard. We've been thinking about this problem for a while (one of our co-founders has been working on this problem for more than a decade). Have ideas? Send us some feedback.