We use XMPP + OTR internally @Infoxchange and it's been really fantastic for us. It's cross platform (although the Windows clients aren't that pretty to be hon

We use XMPP + OTR internally @Infoxchange and it's been really fantastic for us. It's cross platform (although the Windows clients aren't that pretty to be honest, but we don't have many machines running Windows anymore), it's reliable, we can run it on site and ensure that secure chats are not logged (i.e. 1 on 1 chats aren't logged, rooms are just for history when someone joins), it integrates with monitoring / alerting and general operational notifications such as alerts or notifications from Nagios, GitLab CI builds, Application releases, Errors discovered in logs, Changes to oncall rosters, 'interesting' stats from load balancers, global notifications, secure file transfers and the list goes on. One thing I keep meaning to get around to implementing for everyone is a web interface for say people that are volunteering / on a temporary device etc...