The part of an e-mail address that appears to the left of the @-sign — termed the "local part" — is subject to different rules than the ones that govern the domain name part of the address, which appears to the right of the @-sign. A protocol is currently being developed to permit the internationalization of all parts of an e-mail address and for all e-mail headers. This extends the functionality provided by IDN, but the IDN protocol cannot itself be used for this entire purpose. Until the new protocol has been finalized, the characters that are permissible in the local part of an e-mail address are restricted to the pre-IDN repertoire. In the interim, it may be possible to discuss "IDN-aware" e-mail software, as long it is clearly recognized that this is only one aspect of fully internationalized e-mail, and that the term "IDN e-mail" is not a clear designation for anything. (See RFC 4952 for further details.)
This article provides a basis for testing the IDN capability an e-mail application in a manner similar to the way the main page of the IDNwiki supports the testing of Web browsers. Clicking a link in the following table will start the composition of an e-mail message to a test address that has been established in each of the eleven new internationalized domains representing the name example.test in the indicated scripts and languages. The addresses may also be typed or copied and pasted directly into the To: line of an e-mail composer. In the latter case, they will only work if the composer has full support for IDN.
There is a difference in the way the e-mail addresses are represented in the links in the two columns of the table. This permits the first in each pair to be directly used by any e-mail agent, while the second may first require special software configuration. Unlike the situation with browsers, however, doing this with e-mail clients may not be easy, if it is possible at all. Many e-mail applications developers are waiting for the full internationalized e-mail protocol to be completed before modifying their implementations.
What to expect
If your e-mail client allows you to dispatch mail to a test address, and it is successfully processed by all the intermediate transfer agents, the destination server will send two e-mail messages back to you. One will be from the example.test domain to which you addressed your own message. The other will be sent from an address @idn.icann.org. The subject line in both messages will be taken directly from your incoming message.
If you receive the message from @idn.icann.org but not from the localized @example.test, you may assume that the IDN labels in the latter address caused some difficulty on the return path. You may confirm this by repeating the test.
It may be of additional interest to test what your e-mail agent does with an e-mail address that includes an IDN, when it appears in the subject line of an e-mail header or the body of an e-mail message.
The email@example.com addresses
| Clickable mailto links,|
should work with all clients.
| For pasting or typing,|
requires full IDN support.
|mailtest@例え.テスト||mailtest@例え.テスト||Kanji, Hiragana, Katakana||Japanese|