As Microsoft continues to evolve its new Security And Compliance Center (SCC) with all global policies and GO TO place, we can imagine in near future ECP being slowly depreciated with protection features.
If you are a consultant or O365 admin for your organization, i strongly recommend start familiarizing with new Security And Compliance Center (SCC), because that where the future is for global tenant policies.
Outbound spam filtering is always enabled if you use the service for sending outbound email, thereby protecting organizations using the service and their intended recipients. Similar to inbound filtering, outbound spam filtering is comprised of connection filtering and content filtering and allows some specific controls to handle outbound messages. Outbound spam filter policy settings types:
Simply follow this instructions from Microsoft to either edit default spam policy or create a new on, but please take additional note of these settings.