It's long been clear to me that the biggest lock-in Microsoft has, at the enterprise level, is not with Windows or personal apps, but with Exchange Server. And the biggest problem there is this: it's good. Enterprises like it. And, since Exchange works only or best with Windows machines, the lock-in extends to much else. Linux and Mac boxes get purged and replaced by Windows ones.

Or so goes the story I hear from folks at big enterprises.

So I'm wondering about alternatives. Not just about applications, but about who's doing what. Is Google using Exchange? Are Sun, IBM or other open-friendly companies? If not, what ways have they found around it? What do they give up and what do they gain?

Feel free to comment below or contact me directly if you're not comfortable posting here.

FWIW, I'm most interested in hearing what big enterprises -- in business, medicine, education, government -- are doing. Because that's where the lock-in is biggest and there are the fewest alternatives.