You may have a lead who unsubscribed themselves from receiving your emails and have now decided that they would like to start receiving them again. Or you may even have a lead who unsubscribed themselves by accident. If you have a lead who would like to re-subscribe, it's very simple to get them back to receiving your emails.
Login to your crm system and find the desired lead. You will notice that the leads name is in red with a stop sign beside their name. Click on the leads name.