I have a client site that uses the Simplenews module with the Mime Mail and SMTP Authentication modules. The subscriber list has a little over 300 email addresses, and when newsletters go out the cron sends out batches of 100 messages per hour. Things usually go off without a hitch, but with the last newsletter one of the batches sent contained blank messages. I have been unable to reproduce the problem. Someone else reported the same problem here:
. . . but has of yet there has been no response, and I'm not convinced the problem lies with the Simplenews module itself. Has anyone else seen anything like this problem?