in the k2.net studio ,I added a Server Mail event to a activity named as "Declined Notification"

right clicked the event and opened the "property" window.
choose "Title"->"Event Item" , converted to "Mail Content" tab page ,
first , write "fanghui@beautybeard.com" in the "From" field,
second,for the "Email address", I chosed "Originator" radio ,
finally, written some info in the "Subject" and "Body" field.

then I start a instance of the process,
the instance didn't produce errors until it arrived the activity "Declined Notification",the error resulted in the following:
first , the state of the instance is "Error"
second, email wasn't sent.

I don't know the reason ,then I changed the property of the Server Mail event as the following :

From: fanghui@beautybeard.com
Email Address : fanghui@beautybeard.com
Subject : regarding your request
Content: Your Email is [{K2.ProcessInstance.Originator.Email}]

from the Content field , maybe you can understand my intension.
I want to send the Originator's Email Address to me as content of a email.
To do so , I can know where is the resource of the error.

I run another new instance of the process ,
as a result ,the instance works normally and I received the email .
the content of the email is :
Your Email is

the [{K2.ProcessInstance.Originator.Email}] is empty !
why ?

I checked the AD Manager only to find the field Email of the Originator is fanghui@beautybeard.com.

but why k2.net process can not get it correctly ?

other functions of the process is normal except this event , exactly, the field "Email Address" of the event.

what is the possible reason .

Your kind reply will be appriated

Thank you