use UTF-8 encoding for plain-text e-mail sending

java/com.sap.sse.mail/src/com/sap/sse/mail/impl/MailServiceImpl.java

@@ -125,7 +125,7 @@ public class MailServiceImpl extends AbstractReplicableWithObjectInputStream<Rep
         internalSendMail(toAddress, subject, new ContentSetter() {
             @Override
             public void setContent(MimeMessage msg) throws MessagingException {
-                msg.setContent(body, "text/plain");
+                msg.setContent(body, "text/plain; charset=UTF-8");
             }
         });
         return null;