There a few reasons a contact could show as unsubscribed when they didn't request it.
- They forwarded the email from their inbox, and the secondary recipient clicked the unsubscribe link. Unsubscribe links are tied to the original recipient. Encourage contacts to use the Forward to a Friend link instead.
- Some inbox filters click each link in your email, and can accidentally unsubscribe people. If the contact knows they didn't forward your campaign, ask them to contact their IT or hosting service about this issue.
- Did you post your version of the campaign on a website somewhere? If someone clicks the unsubscribe link on a shared campaign, it will remove the original recipient from the list. Set up a MailChimp archive to protect against this.
- Did another account admin accidentally unsubscribe someone?
To resubscribe a contact, they'll have to opt back in to receive your campaigns.