Nri required to file it returns

I am an NRI maintaining my NRI days for the past 10 years.Sea man sailing with a foreign company. I have an NRE salary account with HDFC bank. In the year 2016-2017 i have made a FD of Rs 40 lakhs NRE- FD.I dont have any income source in India.

I have never filed any IT returns in India

Last month i received an e-mail from the IT dept;

 Type:Non filing of IT returns.

Verification issue: Investment(NINO3).

My query;

1)  Am i required to file IT returns?