I just installed the newsletter module v1.2 on my v4.1.8 installation. I activated it on the modules page, then used the Admin link to use it. I get a screen that lets me set up an email (with HTML & TEXT bodies) -- so far so good. When I hit the SEND button, a new page loads with the "Send Newsletter" title on the page, but nothing below. An empty page. And nothing gets sent. I've looked at my server error logs, but there are no error messages. Help!
My first question would be, "Do you have any registered users that ARE actually subscribed to receive newsletters?" The first thing the module does is get users that are subscribed. If there aren't any, then of course it's not going to send an email to nobody.
Similar problem for me on 4.1.9 developer. I'm not getting my new listing notifications anymore, so I logged in to send a quick test email via newsletter to our admins - I get an empty page with "email members" when I try to send the test. No error or confirmation, just the empty page.
If you haven't made any changes to your script and this has just started happening, you may want to check with your web hosting service. Both of these issues revolve around the same functionality of being able to send mail. Many web hosting services (to increase security) often "upgrade" their servers as preventative measures to help thwart SPAM. Inadvertently sometimes also result in blocking emails being sent by your legitimate scripts. It has happened several times to me.