As Salaamu Alaikum Wa Rahmatullahi Wa Barakatuh! Insha Allah this finds you close to Allah & in the best of health and Iman.
'Abdul-Qaadir al-Jeelaani said:
'' If someone only greets you with the words "Salaam" then do not greet them back, rather let them know it's not an Islaamic greeting (i.e. they should instead say assalaamu alaikum)
(Aadaab ash-Sharee'ah v. 1 p. 436)