First of all, thanks for this plugin. I have a problem when I send mails with a subject with too many words. When I test, the confirmation sentence (“Test emails sent to test 2 subscribers”) appears but I don’t receive the mail.
Is it possible the length of the subject is the cause ? When I test with a smaller subject, everything is allright.
It can be a problem of your mail server, the plugin has not limits. Some old system are not able to manage a line length more than 998 characters, but there are system even worse which has the classical 78 characters limit.