SFM eliminates spam by reversing the paradigm of electronic mail, while retaining its traditional simplicity and convenience. With the old paradigm, your E-mail address provides a global point of contact, whereby anybody knowing it is allowed to send you a message. The system is inherently open, which means that there is no effective way to keep spam out of your mailbox. With SFM, your contacts receive different (personalized) E-mail addresses of yourself confined to those contacts. This eliminates address harvesting by rendering it futile.

When you subscribe to SFM, you set up one or more "advertised" (official and global) E-mail address(es) of yourself that can be used by anybody willing to contact you for the first time. This is done in a way that renders the advertised address unusable for harvesting and spamming. A human sender of a message arriving at such an address will be (automatically) assigned a personal address (alias) of yourself restricted to that particular sender. If needed (in truly exceptional circumstances), you will be able to revoke or modify your aliases via a simple Web interface.

There are two reasons why an alias is immune to spam. First, it isn't published but presented to a single contact (which also can be a group of people). Second, it is restricted to the specific contact (a narrow population of senders). This is accomplished by associating with the alias the list of authorized sender addresses, i.e., legitimate sources of incoming E-mail The actual procedure is completely automatic and goes as follows.

After an alias is created, it remains open for a predetermined amount of time (typically 1 week). During that time, it will accept messages from everybody adding their senders to the list of its legitimate contacts. Then, when the open time expires, the alias becomes closed. From this point on, it will only accept E-mail from the senders on its contact list.