[exim] dns timeout

my mail server was not able to connect for several days
and now all mail gets bounced back.
in the return message i get


A message that you sent could not be delivered to one or more of its
receiplients. This is a permanent error. the following address(es)
failed:

wally@???
host lookup for mail.implicit.com did not complete (DNS timeout?):
retry timeout exceeded


all smtp mail is handled by my smarthost router
how can i reset so exim will start trying to route mail again?