This is very strange, since it means the delivery engine ended its work successfully. Try to see if you have a wp-content/log/newsletter with some log file. Probably not, but if there are files, please zip them and send them at stefano@satollo.net (you can write to me directly to continue about this problem).
But for debug next events, go to diagnostic panel and enable the logging at info level, so common actions taken by Newsletter will be logged.
I don’t know about bluehost mail limits, can you ask them if they blocked the outgoind email for any reason?
If you enabled the email tracking on feed by mail, did you see some opening on statistic page?
Stefano.