I’m a new user. Can someone please explain how this Conversation View is supposed to work? There seem to be three options - Show in all views; Show in message detail only, and Disabled. I’m not sure what the first two actually mean but I have tried all three and there seems to be absolutely no difference in what I can see on the screen, whichever option I choose.
In all views, conversations are shown in the message view pane and in the message listing pane with the message list showing grouped messages combined into one line (e.g., sender1, sender2, you). If the message detail option is selected, the message listing pane will show an entry for each message received, while still showing conversations on the message view pane. The no conversation option shows each message individually in both panes.
You might see no difference because you don’t have any conversations.
In that case I may have misunderstood what Conversations are. I thought I had plenty. In Outlook (from which I am trying to tear myself away) a Conversation includes my replies as well as other people’s contributions to a subject. Is that what the little number in a grey box beneath the date or time is all about?
Unlike Outlook, the conversations are shown as different messages in the message viewing pane, whereas Outlook shows the different messages in the listing, but only one message (the selected message) in the listing pane. The idea was to emulate basically what gmail has done. The numbers you mentioned represent the number of messages in the conversation. You will note that on the message view pane, there is a message saying “Show X older emails” (see picture). By clicking this. other message s in the conversation will be displayed. 
Got it! Thank you. I now understand, and can 't expect my own replies as part of the conversation. That’s fine, and thank you for your help.
Actually, your messages are part of the conversation.