Related Clues:

• Virtual inbox filler
• Postal alternative
• Something you click to open
• Deliver spam
• Send, on a computer
• Cyber-missive
• It might have an attachment
• Inbox contents
• Hit "Send"
• Inbox buildup
• It's often filtered
• Modern means of relaying jokes
• Spam, sometimes
• Alternative to the post office
• Unstamped letters