public static string EscapeIdnDomain(
	string email
)

Public Shared Function EscapeIdnDomain ( 
	email As String
) As String

Parameters

email

Type: SystemString
E-mail address string.

Return Value

You can use this method to get an international e-mail address string in SMTP friendly format (called Punycode). It's safe to use this method for addresses which don't contain any international characters, you'll just get the same output as input.

This method converts "user@яндекс.рф" to "user@xn--d1acpjx3f.xn--p1ai". Only domain part (after "@") is converted.

If you have an EmailAddress object (not just a string) which you want to convert, you can use ToIdnAddress method instead.

Note
Punycode works for domain part only. See ToIdnAddress method documentation on how to deal with e-mail addresses having international chars in username (not just in domain).

Reference