Email reply answers crossword

A clever crossword clue!

I'm assuming the answer is a type of email reply. Here are a few possibilities:

• RE (a common abbreviation for "reply")
• RSVP (a less common abbreviation, but still a valid email reply)
• ACK (short for "acknowledgment" or "acknowledged")
• NAK (short for "not acknowledged")
• CC (short for "carbon copy", but also used to reply to an email)

If none of these fit, please provide more context or letters from the crossword puzzle, and I'll do my best to help you out!