We are experiencing intermittent issues with users sending attachments. We are using Exchange 2003/Outlook 2003. Problem attachments are not of any particular type or size. Have successfully sent files larger than the problem files and with the same or different file type. When sending the attachment through Outlook, the message "Outlook is trying to retrieve data from the Microsoft Exchange Server server.domain.com" then get a message saying that there is no connection to the mail server. Server pings successfully. RPC Pings successfully. Attachments WILL send successfully through OWA. Have completely uninstalled antivirus and tested with the same results. Any ideas of what may be causing the issue or what a resolution may be?