[CentOS] yum-cron / email sending problem

I want to use yum-cron with email notificaton.

The upgrade runs, but i get no message. yum-cron aborted with this 
message:

[root at h1 yum]# yum-cron
Traceback (most recent call last):
   File "/usr/sbin/yum-cron", line 711, in <module>
     main()
   File "/usr/sbin/yum-cron", line 708, in main
     base.updatesCheck()
   File "/usr/sbin/yum-cron", line 631, in updatesCheck
     self.installUpdates(self.opts.update_messages)
   File "/usr/sbin/yum-cron", line 582, in installUpdates
     self.emitMessages()
   File "/usr/sbin/yum-cron", line 694, in emitMessages
     map(lambda x: x.sendMessages(), self.emitters)
   File "/usr/sbin/yum-cron", line 694, in <lambda>
     map(lambda x: x.sendMessages(), self.emitters)
   File "/usr/sbin/yum-cron", line 227, in sendMessages
     msg = MIMEText(''.join(self.output))
   File "/usr/lib64/python2.7/email/mime/text.py", line 30, in __init__
     self.set_payload(_text, _charset)
   File "/usr/lib64/python2.7/email/message.py", line 226, in set_payload
     self.set_charset(charset)
   File "/usr/lib64/python2.7/email/message.py", line 262, in set_charset
     self._payload = self._payload.encode(charset.output_charset)
UnicodeEncodeError: 'ascii' codec can't encode characters in position 
209-210: ordinal not in range(128)

whats happend please?