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In SMTP only the envelope headers are really required to be unencrypted. The rest, including the actual To, From and Subject fields are part of the payload. Yo
by kikoreis 8y ago
In SMTP only the envelope headers are really required to be unencrypted. The rest, including the actual To, From and Subject fields are part of the payload. You can use milters that look at the payload which can affect email delivery (think anti virus) but that is separate from the protocol itself.
- pas 8y agoThe "envelope headers" are not really part of the email though, they are just SMTP protocol messages (commands) required to get to the point where you can pipe/stream the actual mail body (payload) through. Though every MTA prepends stuff to the payload (Received headers, etc.).