To clear your outgoing mail queue on your Windows server with Mailenable:

-> Login in as administrator or admin account
-> Open the MailEnable Management directory
-> Now expand servers.
-> Expand localhost and select Connectors.
-> Select quesues from one of the Connectors
-> Select the Inbound or Outbound queue and wait for it to populate.
-> To clear the queue, remove the files
-> Close it
-> You are done

hope this helps.