Going further: Use more Mail tools to manage your messages

By default, Mail lists only the most recent message in a conversation, also known as a thread (messages replying to each other with the same subject). The total number is shown in blue below the date, with a double chevron that you can click to list them all. In the preview, or when you open a message, you can scroll down to see previous messages. This is separate from any quoting within replies; to minimise scrolling, Mail collapses quoted text with a ‘See more’ link.

If you turn off View > Organise by Conversation, messages in threads are