In the exim logs the following error is occur while trying to send an E-mail.
R=lookuphost T=remote_smtp: retry time not reached for any host after a long failure period
To resolve the above errors follow the followings steps carefully.
cd /var/spool/exim/db
Now delete the files or rename it
rm -f retry retry.lockfile wait-remote_smtp wait-remote_smtp.lockfile
or
mv retry retry-back
mv retry.lockfile retry.lockfile-back
mv wait-remote_smtp wait-remote_smtp-back
mv wait-remote_smtp.lockfile wait-remote_smtp.lockfile-back
Restart the exim service
/etc/init.d/exim restart
or
service exim restart
