Gmail groups all replies with their original message, creating a single conversation or thread. Replies to emails (and replies to those replies) are displayed in one place, in order, making it easier to understand the context of a message — or to follow the conversation.
When you open one message in a conversation, all of your related messages will be stacked neatly on top of each other. Each new message is stacked on top of the ones that arrived before it, so that the newest message is always the one you see first.
To see all the messages in a conversation, click the "Expand all" button.
A conversation will break off into a new thread if the subject line of the conversation is changed, or if the conversation reaches over 100 messages.
Turn Conversation View on or off
You can change this setting so that replies aren't threaded into conversations, but appear as individual messages in your inbox.
- Open Gmail.
- Click the gear in the top right.
- Select Settings.
- Scroll down to the Conversation View section (stay in the "General" tab).
- Choose Conversation view on or Conversation view off.
- Click Save changes at the bottom of the page.