Explanation
Sender Policy Framework (SPF) is a simple email-validation system designed to detect email spoofing by providing a mechanism to allow receiving mail exchangers to check that incoming mail from a domain comes from a host authorized by that domain's administrators. n a Small Business Server environment, you may have to prevent your Microsoft Exchange Server-based server from being used as an open relay SMTP server for unsolicited commercial e-mail messages, or spam.
You may also have to clean up the Exchange server's SMTP queues to delete the unsolicited commercial email messages.
If your Exchange server is being used as an open SMTP relay, you may experience one or more of the following symptoms:
The Exchange server cannot deliver outbound SMTP mail to a growing list of e-mail domains.
Internet browsing is slow from the server and from local area network (LAN) clients.
Free disk space on the Exchange server in the location of the Exchange information store databases or the Exchange information store transaction logs is reduced more rapidly than you expect.
The Microsoft Exchange information store databases spontaneously dismount. You may be able to manually mount the stores by using Exchange System Manager, but the stores may dismount on their own after they run for a short time. For more information, click the following article number to view the article in the Microsoft Knowledge Base.