The subscribers can not received e-newsletter even ADMIN.

The subscribers can not received e-newsletter even ADMIN.
My mail server helper check it and let me post it to you:
Hello! This is something you'll need to get a developer (likely the plugin developer) to assist with, its an issue with the plugin. Error you're getting is:
+++ 1WYxp6-0003ba-0u has not completed +++
2014-04-12 07:18:20 1WYxp6-0003ba-0u H=(xn--qby382b.tw) [173.254.121.78]:40157 F= A=dovecot_login:wooweb@xn--qby382b.tw rejected after DATA: there is no valid sender in any header line

Its sending out broken headers.

how can I do?