can not send mail in purchar

can not send mail in purchar

can i help you ?
      I have configuration email and test user send mail outsite insite ok
      I have case
      i enter  Purchase order choose Action/Send email Vendor.      
 
http://www.manageengine.com/products/service-desk/help/adminguide/contracts/contracts-notify-vendor.html
 
      But when send mail notice Sending notification failed.
      
      If login as administrator i can send mail to vendor ok