Maria,
If you know how to move a message, you should be able to mark the items not as spam. In the same context menu as move, you will find some thing labeled junk (I apologize that I do not know the shortcut keys). Once you highlight junk press enter. I believe four options will appear and what you want is to select never block sender‘s domain. A dialog box will appear and all you will need to do is tap through it until you select OK. At that point all groups that I owe should stay in your inbox instead of going to the junk email folder.
The other issue could be your own Internet service provider. I have an old Hotmail style email address and it will not except most groups that I owe addresses. Even if I do the above procedure, it still will not except new groups.io emails. As a result, I created another email address and most groups that I owe messages I receive go to that email without any issues.