The only automatic way someone can unsubscribe from your Artful Mail newsletter is by clicking on the Unsubscribe link at the bottom of your sent newsletter.
If your friend happened to Forward your newsletter to someone else, it is possible that that person clicked the Unsubscribe link.
The unsubscribe link would still be active in the forwarded newsletter.
Therefore, the person who originally was sent the newsletter is the one that would be 'unsubscribed', not the person it was 'forwarded' to.
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