Similar to ドメインキー

DomainKeys Identified Mail

S/MIME

Sender Policy Framework

Bounce message

Backscatter (email)

Internet abuse

Mailto

Sieve (mail filtering language)

VCard

AppleSingle and AppleDouble formats

.eml

Media type

Email address

Automatic Certificate Management Environment

IPsec

Online Certificate Status Protocol

QUIC

Secure Hypertext Transfer Protocol

Simple Authentication and Security Layer

Cryptographic Message Syntax

Email authentication

Bitmessage

DMARC

POP before SMTP

Sender ID