We've got mail accumulating in our Leopard Server's queue and not sure exactly why. This machine has required little maintenance over the years so I'm hoping someone here spot the obvious and save us some time. Let me know what other information would be helfull. Server appears to be functioning normally except for "clogged" queue and the following error associated with each "trapped" message:

Looking at messages in the queue each one states something like this:

Message ID: 4213C3B8B3F
Date:   	October 27, 2009 11:33:27 AM
Size:   	1824
Sender: 	[email protected]
Recipient(s) & Status:
----------------------
[email protected]:
    connect to 127.0.0.1[127.0.0.1]: Connection refused

Under Settings>Relay we have checked Accept SMTP relays only from these hosts and networks:

127.0.0.0/8
10.0.1.0/24

The mail in queue is addressed to users whose accounts are on this server. Mail.app on the client appears to be functioning normally and checking checking mail on the server. We did add a virtual domain some time ago but all that was working fine for some time... This just started happening recently...any ideas?

Edit: toggling the filter services on and off seems to have fixed this except for 2 remaining queued messages that show "mail transport unavailable" as an error!?!