6.2.1 Manual unsubscriptions management
You can decide manually to send or not send newsletters to a single Contact, Account and/or Lead by means of the “Receive Newsletter” field (enabled by default). In this manner, no further newsletter campaigns will be sent to the email address in question.
Alternatively, by means of the OTHER button located at the top right of each record detail view, you can click on the DISABLE NEWSLETTER RECEPTION button.