On subscribing to an email mailing list, modern email recipients have a standard set of expectations. That the email content will match the expectations set on signing up, that their privacy will be respected, and that they have the option to unsubscribe at any point via an easy to locate the link in every sent email. In particular, the ability of contacts to easily unsubscribe is a large part of what makes an opt-in mailing list trustworthy.
When a contact unsubscribes from a mailing list, their status is changed to 'Disabled'. Unlike spam complaints and hard bounces, these contacts can not be updated to 'Active' status. They must resubscribe or be added manually to a list to be used for a future campaign. Use this report to view contacts and email addresses that have unsubscribed during a campaign.
Go to Campaigns -> Campaigns List, select the campaign that has already been sent and click Reports at the right of the campaign card.
An Overview page with campaign detailed information open. Click Unsubscribes at the top of the page to see a report.
Here you can review unsubscribes by hours and all unsubscribed contacts.