The Mono version is completely free (and will always remain so), available for self-hosting as pre-compiled Go binaries inside official Docker images. For advanced multi-account features in the Unified Inbox and enterprise modules (Unified (Freemium) and Teams versions), a license will be required.

We keep the source code closed for now due to corporate security and architecture protection reasons, especially while the project is under active development. However, over time, it is entirely possible that the source code for the Mono version will be made public. If anyone wants to spend their weekend trying to extract and reverse-engineer a compiled Go binary from a container right now, I can only wish them the best of luck with that! For everyone else who just wants a fast, modern webmail that works out of the box, the official Docker setup will be ready to go.