After the deal was formerly announced, the following tweet popped up from George Zachary, who led the original investment in Yammer for Charles River Ventures:

That’s a big claim, considering that Zachary has been a venture capitalist since the 1990s, with a track record that includes such companies as Millennial Media (MM) and Shutterfly (SFLY). So I briefly spoke with Zachary, who is vacationing in the Caribbean. What follows is a transcript of our conversation:

FORTUNE: Most meaningful success in your career. Why?

Zachary: Because [Yammer founder and CEO] David Sacks and I were very close friends before we got into business together, and it’s great to be able to back a friend from the beginning and watch him and his company succeed.

So when CRV first invested in Yammer, was it mostly about David or the idea?

Well, Yammer came out of Geni, which we had funded and is now profitable. David and I were talking about Twitter, and we talked about how useful something like that would be inside of a company. People were all working in their cubicles, stuck with just their inboxes for communication. I remember the moment when we first talked about changing that, creating something like Twitter for business environments, and the spark and sense of excitement we felt.

So is this the largest return you’ve ever generated as a VC? 

It’s slightly over a $200 million gain to CRV [on around $12m-$15m of total investment], but I had a $330 million gain in the 1990s. So it’s not the biggest, although from a quantitative perspective it puts me at over $1 billion of gains in my career.

Yammer raised its final round of venture funding early this year at a valuation reported to be just half of what Microsoft is paying. Are you surprised at the sale price?

No, I’m not surprised at all. We were beginning to see exponential user increases, and were hearing directly from CIOs that they could see decreasing their use of Outlook and increasing their use of Yammer.

Any worries about what will happen to Yammer inside of Microsoft?

You never know what will happen inside of a large company, but Steve Ballmer met with David and they both are incredibly excited. They both know that Outlook has to change and I think, over time, that there will be a combination of Yammer and Outlook. Before that, Yammer will be integrated into SharePoint.

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