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RFC 5321 limits email addresses to 7 bit US-ASCII encoding. RFC 6531 (a fairly new spec) allows email addresses in SMTP commands and IMF headers to be encoded in UTF-8. This SMTP extension makes internationalized email addresses (e.g., pelé@example.com) possible.

An SMTP server advertises support for internationalized email by replying to the EHLO command with the SMTPUTF8 keyword:

250-smtp.example.com at your service

An SMTP client utilizes this extension with the MAIL command:

MAIL FROM:<pelé@example.com> SMTPUTF8 

Question: Are there any SMTP servers or email clients that support SMTPUTF8?

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Not according to WikiPedia. –  Ladadadada Jan 17 '13 at 13:16
I've read that, thanks, but WP is not always current. :-( –  james.garriss Jan 17 '13 at 13:26
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1 Answer

up vote 0 down vote accepted

As far as I can tell, at this time (Feb 2013) there are no SMTP servers or email clients that support SMTPUTF8.

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