SPF means "Sender Policy Framework". The home page for this technology is spf.pobox.com. This FAQ will only provide a short outline of this technology. You can find more information about the technology by this home page if you need further detail.

SPF technology was designed to make the sending of spam/virus messages with faked domain names more difficult. It is like "reverse MX" DNS record which identifies a domain name with a server from which this domain sends its messages.

Example:

• AOL publishes an SPF record which specifies from which computers messages like SomeUser@aol.com can be sent from.
• Once mail server for Icewarpmailserver.com receives any message sent as SomeUser@aol.com, it checks the SPF record of the aol.com domain and compares the IP address from which the message was sent with this SPF record.
  • If the IP or corresponding hostname is included in the SPF record of the AOL server, Icewarpmailserver.com server receives a message without a problem
  • If the IP or corresponding hostname is not included in the SPF record of the AOL server, Icewarpmailserver.com server can handle this message according to the settings on this server. e.g. it can mark the message as spam.

You can look here to see how you can enable checking of SPF record during mail processing in Icewarp.