[StalwartLabs]

> These tools do not integrate with anything; in the case of Stalwart (the only JMAP server not in "experimental" status) you can't just install a JMAP server attached to an existing email service; you have to hand it complete control of everything, even unto the on-disk storage of mail.

This point you mention is being improved. The next release of Stalwart JMAP (expected in one or two months) will delegate user management to either a SQL database or an LDAP directory. Messages will be stored in either Maildir or MinIO/S3. And all other information will be in either SQLite or FoundationDB. All these features were already implemented except MinIO/S3. Development progress can be tracked at https://github.com/stalwartlabs/mail-server/tree/main/crates...