International email

internationalized domain names and address localpartsInternationalized email
International email arises from the combined provision of internationalized domain names (IDN) and email address internationalization (EAI).wikipedia
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Email

e-mailelectronic maile-mails
The result is email that contains international characters (characters which do not exist in the ASCII character set), encoded as UTF-8, in the email header and in supporting mail transfer protocols.
International email, with internationalized email addresses using UTF-8, has been standardized, but it has not been widely adopted.

Email address

e-mail addressemail addressesEmail Address Internationalization
The most significant aspect of this is the allowance of email addresses (also known as email identities) in most of the world's writing systems, at both interface and transport levels.

ASCII

US-ASCIIAmerican Standard Code for Information InterchangeASCII code
The result is email that contains international characters (characters which do not exist in the ASCII character set), encoded as UTF-8, in the email header and in supporting mail transfer protocols.

UTF-8

65001Unicode (UTF-8)AL32UTF8
The result is email that contains international characters (characters which do not exist in the ASCII character set), encoded as UTF-8, in the email header and in supporting mail transfer protocols. International email, by contrast, uses Unicode characters encoded as UTF-8 - allowing for the encoding the text of addresses in most of the world's writing systems.

English alphabet

modern English alphabetEnglishalphabet
Traditional email addresses are limited to characters from the English alphabet and a few other special characters.

Latin script

LatinLatin alphabetRoman script
The same is clearly true of Chinese, Japanese and many other nationalities that do not use Latin scripts, but also applies to users from non-English-speaking European countries whose desired addresses might contain diacritics (e.g. André or Płużyna).

Diacritic

diacriticsdiacritical markdiacritical marks
The same is clearly true of Chinese, Japanese and many other nationalities that do not use Latin scripts, but also applies to users from non-English-speaking European countries whose desired addresses might contain diacritics (e.g. André or Płużyna).

Unicode

Unicode StandardUnicode Transformation FormatThe Unicode Standard
International email, by contrast, uses Unicode characters encoded as UTF-8 - allowing for the encoding the text of addresses in most of the world's writing systems. (Chinese, Unicode)

Hindi

Hindi languageHindi-languageStandard Hindi
अजय@डाटा.भारत (Hindi, Unicode)

Ukrainian language

UkrainianUkrainian-languagemodern Ukrainian language
квіточка@пошта.укр (Ukrainian, Unicode)

Greek language

GreekAncient GreekModern Greek
θσερ@εχαμπλε.ψομ (Greek, Unicode)

German language

GermanGerman-languageGerman-speaking
Dörte@Sörensen.example.com (German, Unicode)

Russian language

RussianRussian-languageRussian:
коля@пример.рф (Russian, Unicode)

Request for Comments

RFCRFCsRequests for Comments
The set of Internet RFC documents RFC 6530, RFC 6531, RFC 6532, and RFC 6533, all of them published in February 2012, define mechanisms and protocol extensions needed to fully support internationalized email addresses.

Extended SMTP

ESMTPSMTPUTF8ETRN
These changes include an SMTP extension and extension of email header syntax to accommodate UTF-8 data.