User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:7.0.1) Gecko/20100101 Firefox/7.0.1 Build ID: 20110928134238 Steps to reproduce: Tried sending a message to domain 壬辰.c0m (0=o). A postfix server refused to accept this message. Sending a message to the matching xn- punycode domain works. According to Wietse Venema http://irbs.net/internet/postfix/0402/2769.html it looks like thunderbird is not converting UTF-8/foreign language letters to 7bit punycode Actual results: message could not be send Expected results: message should be delivered to MTA