No email queue

Yes, and this is very annoying. I have just recently started to use this. Do previous versions have this as well?

Been awhile since I've worked on this module, but I just setup a fresh install with Group 3.3.5 and I'm able to recreate this issue. Looking into it.

My bad; I stand corrected. This is working for me. My configuration had a permissions issue -- after I granted the member permission to view group nodes, I started getting notifications of new and updated group content. Can you tell me more about your configuration?

I...
- created a new group type;
- enabled Group node (on Basic page);
- configured that to send notifications ("Toggled") and selected "Email all group members";
- added a group type role, called it "Members";
- granted that role "Entity: View any content item entities" permission under "Group node (Basic page)".
- created a new group and created a new user;
- added user to the group, and assigned them to the "Members" role.

That user is now getting notifications when I create new or update existing nodes.

I'm using the SMTP module for mailing.

The problem is not that notifications are not created or sent. But it seems that they bypass the queue. Therefor, for several hundred notifications, in my case it leads to an overloaded server.

When you say bypass the queue -- are you using the queue_mail → module, or how exactly are you handling site-generated email?

Using group notify, mail safety, queue mail en SMTP mailer.