What exactly can I conclude from "High scoring spam message has been dropped (in reply to end of DATA command)"?
Solution 1:
When your machine wants to submit an email to the receiving MX server, this is a process of several steps.
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Connecting. Theoretically, a receiving MX server may even refuse a connection from your sending server, for example, if your sending server's IP was on a blacklist. If you pass this and are allowed a connection, next step is
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Handshaking. Your machine is supposed to send a HELO / EHLO, receive a list of capabilities of the receiving server and act accordingly. It may be that the receiving MX server does not like something it sees and terminates the connection. After you have passed this, your machine will send the so-called Envelope informattion, which containes especially two header fields:
- FROM: the sender's email address
- RCPT TO/CC/BCC: the receiver's email address(es)
This is where many connections will get terminated by design, for example, if you try to submit an email to the MX server with a recipient the receiving server does not handle or relay for. This usually results in some kind of "relay not permitted" error.
If your connection is not yet terminated up to here, your machine will start the DATA command and submit the actual content (body) of the email.
This is in your example where it breaks.
So in other words: The receiving MX does not like something in the body content of the mail being sent.