Is there a way to process incoming emails to a particular account, it seems there is an Email Inbound Activity in Classic (https://final-docs.campaign.adobe.com/doc/AC/en/WKF_Repository_of_activities_Event_activities.html#I...). Anyway we can process emails from an inbox.
Use case is to be able to unsubscribe profiles if they email a specific email address.
The link you are referring to is from Campaign Classic.
If that is intended, you may use the activity.
Though it's not to process any "arbitrary" mailbox but rather the mailbox exclusively assigned to be used by Campaign.
In Campaign Standard unfortunately you can't do so.
Mail processing needs to be done outside of ACS.
ACS only supports "standard" mail handling for bounces / feedback loops