Abbr. on top of some e-mails

• Abbr. in an email
• E-mail add-on
• Secretly keep in the email loop, briefly
• Email add-on
• Include without notifying others, in a way
• Emailing option
• Stealthy email letters
• Surreptitiously email
• Include in an e-mail without other recipients knowing

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