IExpense Approval through Email via phone

Currently use R12.1.3 and our business users approve iExpense through email (Lotus Notes).  Users have received Workflow Notification below when approving expense reports through email using their phone.  Why wouldn't the template copy in the response when the user uses their phone versus when they use their laptop or desktop?

"Messages sent to this account are processed automatically by the Oracle Workflow Notification Mailer. The message you sent did not appear to be in response to a notification. If you are responding to a notification, please use the response template that was included with your notification. Take care to include the 'NID' line of the template in your reply. If you are not responding to a notification, please do not send mail to this account.