A Web-based e-mail service from Microsoft that is available free or paid, based on message storage and attachment capacity, security and other features. Originally developed by Hotmail Corporation and acquired by Microsoft in 1998, Hotmail became the fastest growing e-mail service on the Web. Hotmail was integrated into the Windows Live umbrella in 2007. For more information, visit www.msn.com. See Windows Live Hotmail and Windows Live.