Unable to send notification

[zwbao]

I have downloaded mail.jar and created ".bpipeconfig" file in my home directory and wrote :

notifications {
  smtp {
    to="bpipe_notification@163.com"
    host="smtp.163.com"
    secure=false
    username="bpipe_notification"
    password="my_password"  // optional
    from="bpipe_notification@163.com"   // optional, defaults to username
    port=25
    events="STAGE_COMPLETED"
    }
}

But, when I run the pipeline, bpipe returns:

====================================================================================================
|                              Starting Pipeline at 2019-05-29 20:40                               |
====================================================================================================

=========================================== Stage hello ============================================
Hello
MSG: unable to send notification to channel bpipe.SMTPNotificationChannel@5e403b4a due to java.lang.NullPointerException: Cannot invoke method format() on null object

=========================================== Stage world ============================================
World
MSG: unable to send notification to channel bpipe.SMTPNotificationChannel@5e403b4a due to java.lang.NullPointerException: Cannot invoke method format() on null object

======================================== Pipeline Succeeded ========================================
20:40:03 MSG:  Finished at Wed May 29 20:40:03 CST 2019

Not sure what is wrong in this step.