I waited to respond to this until I ran the dailymail one more time. Here are the situations I have had it fail with:
1. Sending text only with PHP sending method - failed after 106 sent
2. Modified cronjob to add -T 0, sent with PHP, failed after 106 sent
3. Changed to SMTP mailing method, stopped after 101 sent.
dailymail appears to send the followup emails on other lists first, then it starts in with my test email to my test list. It stops on different email addresses on my list, never the same one each time. The SMTP log option is turned on, but the filesize is 0 for them - the mailing on today (12/27) has a blank log.
One more thing - I noticed yesterday that when you do resume the mailing, it sends to the one that it stopped on twice. I have the test list setup as a1@website.com, a2@website.com, through a500@website.com. Today it stopped at a84@website.com (after 27 followups sent), I resumed the mailing, and received a total of 501 emails - two of them to a84@website.com.