List two purposes of good email subject lines

A good email subject serves many purposes.

Explanation:

It helps to grab attention If the recipient is someone who receive hundreds of email every day, the chances for your email getting left out is more. If your mail has a catchy subject line it seeks the attention of the reader and increases the chances of the recipient reading your mail. It precisely gives an idea about the whole content of the email. A well written subject line clearly answers the basic questions about the email content.  This will make the reader want to read the whole email.