X-Sender: custom field corresponding to the SMTP sender.
X-Receiver: custom field corresponding to the SMTP receivers.
From: sender email address.
To: receiver email address.
Cc: this field is used by the sender to send an email to different people.
Reply-To: If a receiver replies to your email directly, the answer will be sent to the “reply-to” address. If this information is not available, the answer will be sent to the “From” address.
Organization: sender’s organization if available.
Subject: email’s subject.
Date: display the rendering date for outgoing messages and the reception date for incoming messages.
X-Priority: This field indicates the priority of the email. It goes from 1 (Highest Priority) to 5 (Lowest Priority). If this information is not available, the default priority is 3 (Normal). If you set X-Priority to 1, it is the highest priority. The Outlook will mark the mail with !.
Message-ID: The message-ID is created by eMill and is unique for each message.
