Transliterated name of your message:
${Message.MailingUtmName}
Web version variable (the "Open in Browser" CTA):
${Message.AccessibilityLink}
Sending date & time:
${Message.SendingDateTime}
Channel unsubscribe link:
${Message.UnsubscribeLink}
Topic unsubscribe link:
${Message.TopicUnsubscribeLink}
For more information on how to use an unsubscribe link, please refer to this article.