RFC4408
RFC4408
- April 21, 2021
- Posted by: Nicola Selenu

Sender Policy Framework (SPF) for Authorizing Use of Domains in E-Mail, Version 1
E-mail on the Internet can be forged in a number of ways. In particular, existing protocols place no restriction on what a sending host can use as the reverse-path of a message or the domain given on the SMTP HELO/EHLO commands. This document describes version 1 of the Sender Policy Framework (SPF) protocol, whereby a domain may explicitly authorize the hosts that are allowed to use its domain name, and a receiving host may check such authorization.
Author:Nicola Selenu
Email Service Providers Handbook
The most comprehensive “Handbook of Email Service Providers“!
SPAMASSASSIN RULES
All SpamAssassin rules in one place, EXPLAINED!
SMTP COMMANDS
& REPLY CODES
All SMTP/ESMTP commands and reply codes in one place, EXPLAINED!
Free DNS Tool
Check the DNS records of your domain with our free DNS tool.
Deliverability Glossary
The most comprehensive Email Deliverability and Marketing Glossary!
RFC4408
Sender Policy Framework (SPF) for Authorizing Use of Domains in E-Mail, Version 1
E-mail on the Internet can be forged in a number of ways. In particular, existing protocols place no restriction on what a sending host can use as the reverse-path of a message or the domain given on the SMTP HELO/EHLO commands. This document describes version 1 of the Sender Policy Framework (SPF) protocol, whereby a domain may explicitly authorize the hosts that are allowed to use its domain name, and a receiving host may check such authorization.
Author:Nicola Selenu
Email Service Providers Handbook
The most comprehensive “Handbook of Email Service Providers“!
SPAMASSASSIN RULES
All SpamAssassin rules in one place, EXPLAINED!
SMTP COMMANDS
& REPLY CODES
All SMTP/ESMTP commands and reply codes in one place, EXPLAINED!
Free DNS Tool
Check the DNS records of your domain with our free DNS tool.
Deliverability Glossary
The most comprehensive Email Deliverability and Marketing Glossary!