Favorite business communication tool?

I’d also love to know from people, which of those seems to integrate best with everything else (or, as much as possible)? Seems that it’s simply impossible to expect EVERYONE to definitely use the determined means of communication – add SMS and email even, basically, into the mix. Add freelancers, remote work, part time, etc. to the team and now you can’t necessarily even *make* everyone use what is decided.

Begging the question, is it possible for an organization to tie some things together so that people can use what they prefer, while it’s all interoperable?