Copied from r/selfhosted as seems interesting enough to share with wider audience.
I’m excited to announce the release of Stalwart Mail Server, a single binary solution that combines the Stalwart JMAP, Stalwart IMAP, and Stalwart SMTP servers into one easy-to-install package.
In response to user feedback, some key enhancements were made. Stalwart Mail Server now supports LDAP and SQL authentication, providing seamless integration with your existing infrastructure.
For single node setups, RocksDB has been replaced with SQLite with the option of using LiteStream for replication. For larger, distributed setups, support for FoundationDB was added, letting you scale to millions of users without sacrificing performance. Additionally, it is now also possible to store your emails in an S3-compatible storage solution such as MinIO, Amazon S3, or Google Cloud Storage.
Other notable updates include support for disk quota, subaddressing (or plus addressing) and catch-all addresses.
Check it out here: https://github.com/stalwartlabs/mail-server
I look forward to your feedback and questions!
IMAP is not proprietary. Gmail does support it though, as does pretty much every email provider under the sun. It has limitations though, and JMAP is one proposed alternative to solve some of those.
Note that I don’t have enough knowledge to emit an opinion on whether it’s good or not. I’m just pointing out a couple facts.