Thank you for your post, and I apologize for the late reply.
Since this runs properly from your local email client, there may be a problem sending out through the SMTP server. Try running it locally again, but switch it to the SMTP server. This may provide a clue. If this works, then access to the SMTP server from the server may be the problem. With most servers, there are some firewall issues or port timing issues, so perhaps setting a Pause/Resume (1 second) script step after each email is sent may help alleviate this problem.
If you have already solved this issue, let us know so other forum users may benefit from your solution.