The announcement came in conjunction with the first upgrade to Exchange Server 2003, Microsoft's e-mail server platform.
The news was hailed by industry analysts.
"When Microsoft originally announced IMF, it said it would only be available to SA customers. Just about everybody they talked to said that was crazy," said Peter Pawlak, lead analyst with Directions on Microsoft, a research firm that tracks Microsoft's moves.
Intelligent Message Filter, an add-on to Exchange Server 2003, is based on the SmartScreen anti-spam technology used by Microsoft's Hotmail service and integrated with Outlook 2003. By adding it to the server, said Pawlak, enterprises can create an additional layer of anti-spam filtering.