The Email Postmark Validation Algorithm enables a client to create an e-mail message with a postmark header. This algorithm also enables a client to validate the postmark property on an incoming e-mail message to determine whether it is spam.
Section 2 of this specification is normative and can contain the terms MAY, SHOULD, MUST, MUST NOT, and SHOULD NOT as defined in [RFC2119]. Section 1.6 is also normative but does not contain those terms. All other sections and examples in this specification are informative.