It is  required, in the USA by the CAN-Spam Act, to allow users to unsubscribe.

Please consider that ESPs searches for unsubscribe links to filter emails that don't have them.

Cendyn CRM allows you to add unsubscribe links or automatic cancelation emails.

We also offer the possibility to link the unsubscribe link to a campaign, mailing (audience) lists, or making a global request for your domain. You can have access to this data through your Control Panel, API configuration, or Webhooks. 

Note
Contacts can be deleted directly or through your API configuration.