Can an email address contain international (non-english) characters?

If it's possible, should I accept such emails from users and what problems to expect when I will be sending mails to such addresses?

Can email addresses have foreign characters?

Gmail can now recognize email addresses that include characters with accents on a letter as well as characters in foreign languages. Both developments make for the first time that Gmail can deal with non-Latin characters in email addresses, according to the company.

What all characters are allowed in an email address?

uppercase and lowercase Latin letters A to Z and a to z ; digits 0 to 9 , provided that top-level domain names are not all-numeric; hyphen - , provided that it is not the first or last character.

Can email addresses have non ASCII characters?

Nowadays, creating email addresses using non-ASCII characters is fortunately possible, as many email servers support the newer IETF standards.

Officially, per RFC 6532 - Yes.

For a quick explanation, check out wikipedia on the subject.