Is it possible to check the reason for Approved Emails with high bounce rates?
Run the following query, paying attention to the last lines of the Event_Msg_vod__c field, to determine the reason for failure.
WHERE Sent_Email_vod__r.status_vod__c in ('Dropped_vod','Bounced_vod')
AND Sent_Email_vod__r.Approved_Email_Template_vod__c = '<Approved Email Template ID>'
ORDER BY Activity_DateTime_vod__c ASC NULLS FIRST
CRM Help Documentation: Tracking Approved Email Activity