There are several SPF libraries available. Many mail servers support SPF natively. Most popular mail servers also have extensions or unofficial patches available.
The SPF project does not endorse any of the software listed below unless noted otherwise. We have not checked all of the software for fitness for any purpose.
Please report SPF-supporting software to the spf-discuss mailing list or by contacting us directly.
Libraries
Mail Servers that natively support SPF
Extensions and Patches for Mail Servers
| Name | Mail Server | Author(s) | Contact |
| Courier::Filter SPF Module | Courier | Julian Mehnle | Julian Mehnle |
| Courier Python Filter | Courier | Gordon Messmer | Gordon Messmer |
| exiscan ACL | Exim <4.52 | Tom Kistner | Tom Kistner |
| Exim patch | Exim 4.43 | nslm | nslm |
| MEFilter | MailEnable | Martyn Keen | Martyn Keen |
| postfix-policyd-spf-perl | Postfix | Meng, Kitterman, Mehnle | spf-devel |
| pypolicyd-spf | Postfix | Scott Kitterman | spf-devel |
| tumgreyspf | Postfix | Sean Reifschneider, tummy.com | see website |
| policyd-spf-fs | Postfix | Matthias Cramer | Matthias Cramer |
| Modular Python Postfix Policy Server | Postfix | Petr Vokac | see website |
| Postfix Policy Server v2 | Postfix | Michael Lang | see website |
| ACL Policy Daemon | Postfix | The Gna! Project | see website |
| Whitelister OCAML Policy Daemon | Postfix | Pierre Habouzit | Pierre Habouzit |
| Qmail Patch | Qmail 1.03 | Christophe Saout | Christophe Saout |
| libspf Qmail Patch | Qmail | James Couzens, Sean Comeau | James Couzens |
| libspf/libspf2 spfmilter | Sendmail | Jef Poskanzer | Jef Poskanzer |
| smf-spf Milter | Sendmail | Eugene Kurmanin | Eugene Kurmanin |
| spf-milter (upstream, RPM, on site) | Sendmail | Mark Kramer | Mark Kramer |
| Python Milter | Sendmail | Jim Niemira, Stuart D. Gathman | see website |
| milter-spiff | Sendmail | Anthony Howe | see website |
| Milter Greylist | Sendmail | Emmanuel Dreyfus et al. | see website |
| PTSMail Utilities (milter) | Sendmail | Phoenix Technologies & Solutions | experts@expertsinunix.com |
| Policy Patrol Spam Filter | Exchange,
Lotus Domino | Red Earth Software | see website |
| smf-spf (milter) | Sendmail | Eugene Kurmanin | see website |
| SPF Event Sink | IIS SMTP Server,
Exchange 2000 | Johan Strand | Johan Strand |
| MailEssentials | Anti-Spam Filter Plugin for
IIS SMTP Server, Exchange | GFI Software | see website |
| Sunbelt Messaging Ninja | Exchange 2000/03 | Sunbelt Software | see website |
Extensions for Mail Clients
Note that performing SPF checks in the mail client is problematic because it is often difficult to accurately obtain the required information from delivered messages.
Other Software that supports SPF
