The software giant will move forward with its anti-spam plans by checking all mails going through its Hotmail and MSN services as well as mail adresses with Sender ID in order to verify if these come from valid e-mail servers.

Sender ID is a proposed technology standard, backed by Microsoft, for verifying an e-mail message's source. It combines two previous standards: the Microsoft-developed "Caller ID," and the Meng Weng Wong-developed SPF.