Notice received from @gmail.com for GSTR 1Vs GSTR3B difference

Hi,

I need one information, we have received 1 notice from GST department for Difference between Gstr 01 vs Gstr 3B from @ gmail.com . They asked to reply to that email for clarification.
I wanted to know that is this fake email or?..
what I want to do now, do I need to reply to that email or shall I leave it.
kindly suggest me what to do