Do Muslims understand the English word "god" specific to be Allah, or at least a neutral word not in exclusive use by any religion? If so, may I assume the God referred in "may God be with you" could be Allah, hence react at ease?
However, if Muslims understand the English word "god" is for Christian use exclusively, what's the best reaction for Muslims when receiving a blessing in pure good will from such different religion?
(Original question was a two-part one that begins with asking if the concept of "may God bless you (be with you)" exist in Islam. That is solved, Thank you.)