Group by subject
If you frequently correspond with a certain person/people, turn on the email thread. To expand or collapse a list of messages in a thread, click the subject of the message.option (to the right above the list of messages). Your emails will be grouped by
The message thread displays all emails grouped by a selected subject, even if they have different recipients or senders, or are in different folders. Messages are only grouped by subject. Senders and recipients do not factor into grouping.
You can also move within a message thread by using the message page.
To ungroup messages, disable theoption (above the message list, on the right).