You can quickly create a task from any email by using More > Add to Tasks
You can create a new task from an email to keep all the relevant details from the email in the task.
To create a tasks:
Click on the More button
Select "Add to Tasks"
The task you create will have a "related email" link so you can easily refer back to the email.
You can also use this method to create an Event from an email (Create an event from an email)