If you regularly compose many emails, use the conversation mode. In this mode, all your messages will be grouped by subject and sender, and the message page will also display other emails from the same conversation.
To turn on conversation mode:
Tap anywhere on the message to view the email chain.
You can also resize the message list to free up additional space for the message text. To enable compact mode:
All other mailbox settings can only be set in the Yandex.Mail web interface.