Netscape Communications Corp. said it received subpoenas from Microsoft Corp. for its employees' electronic mail, an effort to cast Netscape negatively as Microsoft prepares to defend itself in an antitrust suit this month. Microsoft, the world's largest software company, last week subpoenaed so-called flame mail from two internal Netscape newsgroups called Bad Attitude and Really Bad Attitude, used as forums for Netscape employees to gripe about everything from cafeteria food to work projects. Microsoft faces a Sept. 23 trial date on allegations to face charges that it tried to stifle competition in the market for Internet browsers. The company might try to bolster its case by using rival Netscape's internal e-mail to show that Netscape's employees think its products are inferior or that its own management was responsible for its decline in the browser market. In a massive technology sell-off on Nasdaq, shares of Redmond, Wash.-based Microsoft fell $9.31 to close at $95.94 and Mountain View-based Netscape fell $5.50 to $18.