I'm using Moodle version 1.9.3 and I'm having a similar problem occasionally. The problem is that the instructor (teacher role) isn't seeing ALL of the e-mails he sends, just some of them. E-mails are NOT being caught in his spam filter - he checks it daily. His e-mail account is activated in his user profile. Any other ideas? (aside from upgrading, which I will do eventually). Thanks.