This document discusses several standards related to email including RFC 5321 and RFC 5322 which define the core email protocols SMTP and message formatting. It also covers MIME which defines content types and transfer encodings used to encode attachments. Base64 encoding is explained as a format used to encode binary data for transmission in email. S/MIME is defined as providing encryption, signature, authentication and secure mailing list services for email and detached signatures are noted as useful for verifying email content without embedding signatures. DKIM is introduced but not described.