Gmail - Reply by Chat

Before you respond to an email, check the footer of the message to see if the other person is online. If they're available, you can save time by clicking "Reply by chat" and get them in real-time rather than over email.

The Reply by Chat feature allows you (and your contacts) to converse about an email message that you have sent or received, in real time.
1. Go to Gmail and log into your account.
2. Open the desired message.
3. Check to see if the contact is online and available.
4. Click the Reply by chat link at the bottom of the message (next to the Reply and Forward links).