Firms that use e-mail for marketing purposes are scrambling to meet a tough deadline this week. On Thursday, the first federal antispam law, the Can Spam Act 2003, goes into effect, and many companies are worried that they'll be caught in noncompliance. The Boston Globe reports today that while the law poses little threat to companies using e-mail for legitimate commercial purposes, it does require a few modifications to how firms present e-mail correspondence that could put some in a bind.