Deleting Scan to Email Attachments from Outlook

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Hi guys

We have a bit of strange problem here

 

We are using Konica MFD which allows staff to send scanned documents directly to email from the MFD Device, we are using Exchange 2010 for all Staff accounts

 

Now recently we have had this problem whereby if users wanted to delete the email with the attachment from their outlook, if they simply select the message and press delete it comes with an unknown error, however doing a Shift / Delete gets rid of the message

 

this only seems to occur with emails sent via photocopier scan to email

 

Any suggestions where to look? Left us baffled

 

funny thing is as Network administrators we don't get this problem seems to be only random regular staff members!