Related Clues:

• Abbr. on top of some e-mails
• 'Return to ___' (Elvis hit)
• Last word in an Elvis song title
• Email header info
• USPS patron
• Abbr. atop some e-mails
• E-mailer, for one
• 'Return to --'
• Include secretly, as in an email exchange
• Include invisibly in an email
• Bring into the conversation, quietly
• Email origin
• Recipient's antithesis
• Return recipient
• 'Return to ___'