In order to increase the deliverability of your emails and to prospect in concert with the GPDR (cf. Understand GPDR), you can add an unsubscribe link.
1.Go to your Sequences, in the Settings tab.
2. In the Unsubscribe section, enable the option "Include an unsubscribe link at the end of each email" and save
If your contacts decide to click on the unsubscribe link, they will automatically be unsubscribed of the current sequence and cannot be added to other sequences anymore. Besides, they will take the following status in the sequence : Unsubscribed.