I am wondering if there is any Salesforce system limit regarding the number of outbound (i.e. towards other systems) API calls that can be made from an org. I am aware of all of the concurrent and 24h-rolling limits on inbound API calls, and would like to know if there exists something similar regarding outbound calls or are they not limited by Salesforce?
API call limit is only for inbound calls. Outbound calls are governed by the per transaction and maximum timeout limits.