A Message-ID is a unique identifier assigned to an email message. It is a header field in the email's structure that helps differentiate one message from another, even if they have the same subject line or are sent from the same address. The Message-ID is generated by the sending mail server and typically follows a specific format, which often includes a combination of the local part (like a timestamp or a unique string) and the domain name of the server that sent the email.
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