Actually there has been an attempt of a state mandated E-Mail service in Germany called De-Mail. The idea was to put guarantees like identity, delivery receipt

Actually there has been an attempt of a state mandated E-Mail service in Germany called De-Mail. The idea was to put guarantees like identity, delivery receipts and stuff into an email system, so it can be used for legally binding communication. However it failed for various reasons (privacy concerns as it purposely had no e2e, usability restrictions, cost, ...)