How to enable DMARC?

Good morning, everyone, I’m new to the community, I’m setting up a VPS server on Locaweb, but the email system works normally to receive but it’s not sending, I’ve read several articles here talking about this problem. it is due to the blocking of port 25 of the datacenter, in my case Locaweb does not release it.

Well come on I need to know if DMARC is active or not and how do I activate it, thanks

Please follow basic instructions How to ask for assistance?