Among the several types of triggers available when you design your own automation workflow, the "When someone unsubscribes from any list" trigger is the one you need to choose when you want to set an automation in motion as soon as someone unsubscribes from any of your email lists.
A. Setting the parameters of the trigger
The only parameter that you need to define on this type of trigger is whether the automation will be triggered for every unsubscription, or whether it will be triggered on the first unsubscription only.
You can choose either option from the available drop-down menu. After you are done, clicking on the Save button will get your trigger ready and waiting inside your workflow.
B. Taking advantage of the trigger
It is important to understand that no actions can be performed on members who have unsubscribed from an email list. So, why should you have such a trigger if you can't perform actions on unsubscribed members? The answer is simple: you can subscribe them to other lists, where you can take advantage of all the available actions. First, make sure that the unsubscribe settings on your account in our platform are set to: "When unsubscribing users from a list, send to them from other mailing lists".
Then you will need to create two separate automations, each one with its own trigger and actions:
Automation #1: When someone unsubscribes from any list, subscribe them to list 'mailing list 1'.
Automation #2: When someone is subscribed to list 'mailing list 1' (because of Automation #1), send them an email campaign, then unsubscribe them from mailing list 1.
By using the above option, you can design your own automation workflow to perform actions on whoever chooses to unsubscribe. It will be easy to contact the people who unsubscribed to say you are sorry they opted for this, or to perform any other type of action from the ones available. Just make sure that you remove them from your second list afterward, since they requested to be unsubscribed after all.