Ouch, I wasn't aware of this, as I haven't used it yet, and my brief poking around the source was mostly focused on the UI. On the plus side, it's open source

Ouch, I wasn't aware of this, as I haven't used it yet, and my brief poking around the source was mostly focused on the UI. On the plus side, it's open source and seems nice inside, so it shouldn't be hard to add support for regular old IMAP or JMAP if one wants.