[exim] relay via gmail

Hi,

using Exim 4.72 in a centos, set up the smtp to relay from gmail, I found
many entries like following in the log:

R=smarthost T=remote_msa defer (-53): retry time not reached for any host

I have to setup a cron job to do:

exim -qff

and it got sent out:

R=smarthost T=remote_msa H=gmail-smtp-msa.l.google.com [173.194.79.108]
X=TLSv1:RC4-SHA:128
2012-08-27 01:15:17 1T5fvw-0007pj-2M Completed

any idea why? Thanks,

Angelo