I have started experiencing some problems with bulk mailing, for at least 3 mailings the mailing report shows successful deliveries greater than the intended recipients. I have checked the detail report and noticed that some contacts actually show successful deliveries 4 times, while others are double or triple - see attached
In some cases, the contact email is marked as on hold but report shows double or triple successful deliveries.
My Mailer Batch Limit is 750, cron used to run every 15 minutes (*/15 * * * * wget -O - -q -t 1 'http://mysite.org/sites/all/modules/civicrm/bin/cron.php?name=username&pass=password&key=site-key'), i have changed it to every hour but still get more deliveries. Mailer Throttle Time, Mailer Job Size and Mailer CRON job limit are set to 0. I have had this settings for long and didn't experience this problem until recently.
I have also taken a look at this post here but this doesn't seem to be my case.
What should i be looking at? Civi 4.6.10, Drupal 7