Taking a new twist on an old antispam method, Microsoft plans to use white lists for its free Hotmail e-mail service.

Days after Yahoo unveiled new mechanisms for controlling spam on its free Web e-mail service, Microsoft sent Hotmail account holders an e-mail that pledged to upgrade its services with the white lists next month, and offered a sneak peak of how the system will work

A white list checks incoming mail against a list of addresses that the account holder has already approved.

The white list, in its purest form, is considered one of the more draconian antispam methods, because mail that doesn't match the list does not get delivered. (Black lists, by contrast, assemble a list of known or suspected spammers, and don't deliver messages from senders who are on the list.)

In Hotmail's version, incoming e-mail from senders that match entries in the recipient's address book are displayed in what Hotmail calls its "Today" page, which greets the Hotmail account holder with basic information about the account--along with a slew of MSN marketing messages.

"Your session will always start on the Today page, where you will only see new messages from people you know," the preview's audio explanation says. "To qualify as someone you know, the sender has to have an e-mail address that is only in your contacts. As a result, you will only see the messages that are important to you first."

Hotmail account holders can then click on their "Mail" tab to find the full contents of their in-box. Hotmail also offers a "Junk E-Mail" folder, where it delivers messages the system suspects of being spam.

Rising frustration at the cost and volume of spam has fuelled a new market for products and services designed to mitigate and manage spam.

The preview came after news of Yahoo's new spam features, which include the option of setting up dummy e-mail addresses when subscribing to services on the Internet, and showed up the same day the U.S. Senate passed a bill that would criminalise spam and set up a nationwide list of people who do not want to receive spam.

In addition to the white list, Hotmail will make it easier for account holders to report spam. Yahoo has focused on its reporting system in order to improve its spam filters, which have dramatically reduced the amount of spam reaching its in-boxes. The Hotmail update will also indicate with a label whether or not messages in the in-box are from the recipient's contacts.

Microsoft promised a preview "soon" of changes coming to its Calendar and Contacts applications.

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