When you want to create a task based on the contents of an email message, you don’t have to re-enter all the information. Instead, click the message and drag it to Tasks on the navigation bar.
The contents of the message, except attachments, are copied to the body of a new task. A task created this way is the same as if you create a task from scratch, except you save time as contents from the message are automatically added to the new task. Just like for any task, you can set a due date, add a reminder, or assign the task to someone else.
Tip: You can also drag contacts, calendar items, and notes to the Navigation Bar to create tasks.
Creating a task from a message versus flagging the message
When you flag an email message, the message appears in the To-Do List in Tasks and on the Tasks peek. However, if you delete the message, it also disappears from the To-Do List in Tasks and on the Tasks peek. Flagging a message doesn’t create a separate task.
By creating a task from a message as described above, the new separate task is independent of the message. If the original message is deleted, the task is still available, including the copied contents of the message.