I’d just like to direct folks’ attention to the r/halowars Discord server. We’re currently making some changes and improvements but it is already the largest Discord server for Halo Wars, serving both Xbox and PC players alike.
Discord itself is an all-in-one text and voice chat service that functions a bit like IRC and Teamspeak. You can join for free, customise your profile and link other accounts to add friends who already use the service. It is available on all desktop and mobile platforms.
Invite link: Discord