Here you'll find SMTPUTF8 support for qmail, sponsored by CNNIC. SMTPUTF8 allows using unicode in email addresses, आर्न्ट@यूनिवर्सल.भारत is a valid email address and it's very simple to implement.

The branch original contains netqmail 1.06.

The branch smtputf8-cleartext contains a patch for (EHLO and) SMTPUTF8 on top of original.

The branch smtputf8-tls contains a TLS patch and a patch for SMTPUTF8 on top of original. Each patch is a single commit.

The TLS patch is old; it's the one from Gentoo linux and probably not something you want to use on other platforms. My patch should apply easily on top of any of the many TLS patches I've seen for Qmail.

My blog contains a posting about postfix, sendmail and this code and a few other relevant postings. The eai-test-messages repository contains some test messages.