Is it really hard to do? Wouldn't it be enough to have the server always set the right MIME headers for messages from a mailing list? And then have the vacation

Is it really hard to do? Wouldn't it be enough to have the server always set the right MIME headers for messages from a mailing list? And then have the vacation mailer not send any out of office replies to mails from mailing lists? This sounds like a problem with a technical solution. From the Sieve vacation RFC https://tools.ietf.org/html/rfc5230#page-8 https://tools.ietf.org/html/rfc5230#page-8 Implementations SHOULD NOT respond to any message that contains a "List-Id" [RFC2919], "List-Help", "List-Subscribe", "List- Unsubscribe", "List-Post", "List-Owner", or "List-Archive" [RFC2369] header field.