Cisco Systems will acquire open source email and calendar software-maker PostPath for $215 million. Cisco VP Charles Carmel says the company will integrate PostPath, usually called an alternative to Microsoft's Exchange, with WebEx software, which Cisco acquired for $3.2 billion in March 2007. It's only big-spending Cisco's fourth buy of the year — for the networking giant, a tightening of the purse. There were zero tech IPOs last quarter and also relatively few major acquisitions. Which means PostPath investors Matrix Partners, Jafco Ventures and Worldview Technology Partners are no doubt gluttonously bathing in the schadenfreude this morning.