We are running SmarterMail 16.3.6754 and have one end-user that is having a sending issue. We can see the user's messages in Spool; however, when we try to force them out, the messages never leave the Spool. The "Next Attempt," time will change, but the messages do not send at that time. When selecting any one of these messages from Spool, then going to Actions > View Recipients, it shows "Error: 0" to the right of each recipient. Any help with this would be greatly appreciated.