Similar to バックスキャッター_(電子メール)

Google Groups

HTML email

Maildir

Mailto

Mbox

MDaemon

MAPI

MX record

POPFile

Riseup

Sieve (mail filtering language)

Sympa

Tuta (email)

VCard

X-Face

X.400

AppleSingle and AppleDouble formats

.eml

Ezmlm

Webmail