@mattyrob - Thank you so much for a wonderful plugin and support.
You're probably tired of hearing about this problem. I read some of the threads that others were having that are very similar to mine.
I'm using the latest version of WP and the latest version of your plugin (just installed it a couple of days ago). The very first time I tested it, everything worked great, but now my tests are not sending automatic emails to public subscribers at all, only registered subscribers. It sends manual emails to public subscribers from the plugin fine, but I'd like to have emails automatically sent when a new post is published.
I contacted my host since I saw that you say it's most likely a problem from the server. I spent a good amount of time talking to them and there doesn't seem to be any limitations, especially since I have a VPS account. I'm stumped as to why it isn't working. I even installed WP Mail Log as you suggested in another post.
Do you have any insight as to why it may not be working? My host asked what the requirements are from your plugin so they can pinpoint what limitation it is we're facing so we can try to fix it.
Thanks for your time, I really appreciate it. I'll make a donation once I figure all this out and get a payment from my client!