If you are a conversation view user, you probably have had the situation where emails are grouped together simply because they have the same subject line.  This can happen a lot if you’re discussing similar topics with lots of people.  Google has now fixed this problem and will keep emails separate if they have the same subject line but, perhaps, different senders. Learn more here : https://gsuiteupdates.googleblog.com/2019/03/threading-changes-in-gmail-conversation-view.html