Emails to Offer Approvers Not Going Out

Summary

Getting message "Due to permission restrictions email to **** did not get sent"

Content

Although assigned offer approver is listed as an offer approver on the requisition, and checked offer approver on their user record, we are getting the message that due to permission restrictions email did not get sent.  Does an offer approver have to be a requisition owner in order to approve via email?  I know they have to be an owner in order to view the offer letter from within Taleo, but that shouldn't stop them from getting the email for approval.  They can still get an email to approve the requisition even though they're not a requisition owner.  ~Linda