Today the MailetContainer is thought to be asynchronous, thus need to explicitly handle failures. The classic way to do this is through 'error' processors, which stores the email in a MailRepository for potential later processing.
However, in an LMTP execution context it makes sense to escalate the failure to the LMTP client. That way the client can requeue the email and plan for a later delivery.
We could have a way to propagate the failure back to the caller:
- It allow avoiding ignoring failures of the error processor
- I allows in a SMTP (asynchronous) execution context to requeue fail mails.
The management of partial failures will need to be explored.