Privately keep in the email loop, briefly

• E-mail add-on
• Stealthy email letters
• Include discreetly, on an email
• Email letters
• Letters in front of an e-mail address
• Send covertly, as a dupe email
• Slyly include in an email, for short
• Discreetly keep in the email loop, for short
• Private attachment, for short

Wiktionary Word definitions in Wiktionary
init. 1 body-centered cubic 2 blind carbon copy vb. to send something by blind carbon copy