Related Clues:

• It doesn't leave a paper trail
• In-box input
• Contacts quickly, perhaps
• Spam, maybe
• Terminal message?
• Stamp saver
• Dot com letters
• It might arrive with a beep
• Contents of some in-boxes nowadays
• Modern missive
• Dot-com communication
• Modern memos
• Spam, for example
• Messages via modem
• Unstamped reply