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Answering my own question: For messages sent today from a Google Apps account to a gmail account, I see that instead of "mailed-by: <domain>", there are now two
by pwinnski 8y ago
Answering my own question: For messages sent today from a Google Apps account to a gmail account, I see that instead of "mailed-by: <domain>", there are now two new headers: "signed-by: <hostname>" and "security: Standard encryption (TLS)" with a link to learn more.
This seems to be about S/MIME support, not MTA-STS support.
- jcranmer 8y agoIn general, with email headers, you cannot trust any of them. The one exception is the Received header added by your MTA, and perhaps other headers if you know your MTA adds them and you know that it will strip any that appear in the original message.
- shereadsthenews 8y agoYou can verify the authenticity of any header that appears in the DKIM signature. That's why you see things like this in the signature: h=mime-version:from:date:message-id:subject:to:x-original-sender :x-original-authentication-results:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-unsubscribe:list-subscribe;