[Exim] Timeout retry issues.

Starting Saturday one of my servers stopped sending outgoing mail. Today I
noticed the server had some 20,000 messages to deliver. Every entry in
exim_mainlog looks like this:

2004-05-24 12:51:37 1BRwA9-0005U5-2S == kurt@??? R=lookuphost
T=remote_smtp defer (-53): retry time not reached for any host

I've restarted the service. When I send email to an account on the server,
it's delivered immediately. The problem seems to be with the outgoing
queue.

Any suggestions?