[Exim] message frozen

can someone tell me what this means? it appears every hour in my
/var/log/exim_mainlog.

2001-09-05 16:23:03 15cpCJ-0000E2-00 Message is frozen

i am using the default configure file with the added to routers:

smarthost:
driver = domainlist
transport = remote_smtp
route_list = "* mail.core.com bydns"

thanks and Peace...................ed