UnsupportedDataTypeException sending email

Seam 3 send mail example fails on:
javax.activation.UnsupportedDataTypeException: no object DCH for MIME type multipart/mixed;
boundary="----=_Part_1_340486764.1311336438303"
at javax.activation.ObjectDataContentHandler.writeTo(DataHandler.java:905) [activation-1.1.1.jar:1.1.1]
at javax.activation.DataHandler.writeTo(DataHandler.java:330) [activation-1.1.1.jar:1.1.1]
at javax.mail.internet.MimeBodyPart.writeTo(MimeBodyPart.java:1476) [mail-1.4.4.jar:1.4.4]
at javax.mail.internet.MimeMessage.writeTo(MimeMessage.java:1772) [mail-1.4.4.jar:1.4.4]
at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:1099) [mail-1.4.4.jar:1.4.4]
... 42 more