Is it permissible to respond to the greeting "So-and-so sends their regards to you" by saying "May Allah keep you and him safe" instead of "Peace be upon him" or "Peace be upon you and him"?

If a greeting of peace (Salam) is sent, it is obligatory to respond immediately to the sender. It is recommended to respond to the messenger by saying, for example: "And upon you and upon him be peace (Wa alayka wa alayhi as-salam)." As for saying: "May Allah grant you and him peace (Allah yusallimuka wa yusallimuhu)," it does not conform to the Sunnah. The Sunnah is to say: "Upon you and upon him be peace (Alayka wa alayhi as-salam)."