Claws mail cannot send email to international domains, smtp server reject recipient address. How to reproduce: try to send an email to any of the test email addresses listed here: http://idn.icann.org/E-mail_test Here is a part of smtp log when i try to send and email to mailtest@пример.испытание 2010-10-24 10:48:40 [21285] SMTP syntax error in "RCPT TO:<mailtest@\320\277\321\200\320\270\320\274\320\265\321\2 00.\320\270\321\201\320\277\321\213\321\202\320\260\320\275\320\270\320\265>" H=(host) [SIP]:52692 I=[DIP]:465 domain missing or malformed Looks like claws should recognize international domain names (IDN) and translate them into Punycode (http://en.wikipedia.org/wiki/Punycode) before sending email.
*** This bug has been marked as a duplicate of bug 1670 ***