OK, I think my problem must be different then. I suspect it goes deeper than the forum plugin, but I'm waiting for our IT person to get back to me on the various issues. 

Thanks so much though, for posting that. I wish my problem were that easy to resolve! 

Kind regards,

Margaret

>All works fine. The problem is in Private Forum. You've created a private forum for testing. You new registered Users "Subscribers" don't have access to the forum you're testing. It seems you've created a topic then made it private or something else. In any case the problem is in forum accessibility to the user you're testing. Make sure the Usergroup of thet user has Standard Access or higher access to that forum, otherwise that user will not receive email notification.
We just set Standard Access in these forums (it's important to set both levels) for your default Usergroup "ASSV Lid" (Subscriber) and this user receives all email notifications without any issue. Then we set "No Access" access to these forums and that user stop receiving email notifications. That's correct and all works correct. User should not receive new topic/post email notification from forums where they don't have access. It doesn't mean they had access before and subscribed before.<

Kind regards, Theo

Thank you! We have just three kinds of access: guest (read only), registered (standard access, this is set as the default), and admin (full access). Is this correct, or do I need to change something?

Thanks again,

Margaret

With the help of WPForo support team it was fixed for my situation. The problem for me was that I did set wrong access level for user groups. Or more precise; I used secondary User group for forum acces instead of (main) user group. Hopefully this information will help you for your situation.

Kind regards, Theo

Thank you so much for these very clear instructions! I'm trying to get the answers to these and as soon as I do, I will post them here. 

Thanks again!

Margaret

Actually, I followed ALL of the suggestions posted in this topic, but none of them resolved the problem. I tested all the plugins - twice - and then downloaded the other plugin you suggested and hired a developer to use that plugin to troubleshoot the issue. He explained that the plugin was of no use (i.e., it didn't help him diagnose the problem) and found the workaround I described above. I agree that I need to figure out what the problem is, but the suggestions here - even when I hired someone more technically skilled than me to implement them - didn't seem to work. If you - or anyone else - have any other ideas, that would be really great.

Thank you 

@margaret Please reply EXACTLY to the following:

1. If you disable wpForo all the email works (new registrations to user, to the admin, lost password). YES OR NO.

2. With wpForo enabled and your DEBUG to a LOG enabled and after a few hours running and doing tests is it EMPTY (located in wp-content). Any errors ? YES OR NO. If any errors post them here.

https://codex.wordpress.org/Debugging_in_WordPress

3. What is "aruba-proxy" web server ? What PHP do you run ?

I'm waiting for an answer.

😎

Thank you 

Yes, please let me know what happens and if anything works! 

Thanks so much,

Margaret

Well all i know is that you didn't follow any of the suggestions posted in this topic.

The important is to find if the email DOESN'T go out of WP for some reason (conflict or error) OR it goes out but never delivered.

Don't get me wrong, maybe you can't do all the suggestions here yourself, still there is no other way.

Thanks so much,

Margaret