Based on the clients report, it seems that the particular client is receiving blank emails only after November 10th( this is the date we made some changes to the code to fix few blank email being sent issue). Encrypting the email content seems to have fixed the issue with some users, but for few it seems seems to be the beginning of the blank email issue.
The main problem is we could not generate the blank emails, We also tested BCC'ing all emails to our gmail, yahoo and usa.com account. And we found that to be working just fine. We have been going through various post/forum and modified the code, We could not take any chance and test with the users(750 emails are being sent). Its working for the majority and for few it creates problem.