mailbourne-core — the vocabulary

Start here. These are the nouns of email that every other crate shares.

The single most important idea in this crate — and in all of email — is the difference between the envelope and the message:

• The [envelope::Envelope] is what the servers read: who to bounce to (MAIL FROM) and where to deliver (RCPT TO). Like the outside of a paper envelope, it is thrown away after delivery.
• The [message::Message] is the letter inside: the headers your mail client shows (From:, Subject:) and the body. The receiving server has no obligation to make it match the envelope — that mismatch is how BCC works, and policing it is what SPF/DKIM/DMARC are for.

Reading order: [address] → [envelope] → [message] → [event] → [config].