Sa4o is email protection software that uses permission-based and Bayesian logic to filter out spam. It offers 9 filtering levels, including SPF, sender's email address, domain, subject, body content, header content, file attachment type, sender's country, and Bayesian method.

One of the best things about SafO is that it imports all addresses from Received & Sent e-mails and also from Personal Contact Books during installation. This ensures that all these e-mail addresses are included in users whitelist so that future messages coming from those will be sent directly to the inbox.
Any messages from unknown senders will be sent to a quarantine folder and the sender will automatically receive an e-mail asking for a name and purpose of the message. Once the sender responds, a pop-up window will appear on the user's screen requesting his approval for that specific sender or message.
SafO provides 9 filtering levels including SPF, sender's e-mail address, domain, subject, body content, header content, file attachment type, sender's country and bayesian method. The software is very intuitive and easy to use. The best thing? The software is now available as freeware!
Version 2.0: now full freeware