E-Mails from blasts do not send and reported as bounced

[cmedia]

E-mails we queue to get sent out through CiviCRM/Drupal are not delivered.  We are not blacklisted, etc.  We did not have an issue with this before but all of a sudden e-mails are simply bouncing one after another for good e-mail addresses.  CiviCRM reports the e-mail blast as having been completed afterwards.  Anyone know of a workaround?  I considered modifying core source code to only associate sendmail with delivery process vs going through QMail but believe this would create more hassles and potential errors.  Any information on this would be greatly appreciated.

[Donald Lobo]

can you check your mail log and see what error messages are being recorded. This should give you/us a big clue on whats happening and why

lobo
 

[ctarascio]

cmedia,
   I doubt this post will be helpful but you never know.
What percentage of you email blast is bouncing? If it's not 100%, you might take a look here: http://forum.civicrm.org/index.php?topic=4167.new;topicseen#new. Keep in mind though, that we are using the civismtp service.

Cynthia

[Denver Dave]

Any chance, this could be the "premature bounce" issue reported with these threads:

http://forum.civicrm.org/index.php/topic,5245.0.html
and
http://forum.civicrm.org/index.php/topic,5810.0.html