Email authentication
（重定向自Authenticated Email）
![Email authentication can be complicated by the presence of an intermediate relay. A and B clearly belong to the author ADMD, while D and E are part of the recipient network. What role does C play?](/Images/godic/202412/22/Email-flow-with-an-intermediate-relay2538.png")
![A schematic representation of the most common ways that an email message can get transferred from its author to its recipient.](/Images/godic/202412/22/Mailflows-reloaded2538.png")
![SPF authenticates the sender IP address.](/Images/godic/202412/22/SPF2538.png")
2538.png")
Email authentication is a collection of techniques aimed at equipping messages of the email transport system with verifiable information. It is a coarse-grained authentication, usually at Administrative Management Domain (ADMD) level, and implies no sort of authorization. That is, the purpose of email authentication is to validate the identities of the ADMDs who participated in transferring and possibly modifying a message. The results of such validation can then be used in email filtering, and can clue recipients in about what kind of reaction or reply a message deserves.