Dears,

we are implementing this mail box to get email from clients and open case for them but as you can see we getting the following error 

An unknown error occurred while receiving email through the mailbox "Web Development ". The owner of the associated email server profile Cases From Email has been notified. The system will try to receive email again later.
Email Server Error Code: Exchange server returned UnknownIncomingEmailIntegrationError -2147204719 exception