How do you identify if a mail you received is from outside Kotak?

 Dear All below article I am using Hindi+Egnlish language.

Aj kal bank ke name pe bahut dokha ho raha hai isko pahchanne ke jarurat hai, nhi to apka bank account khali ho sakta hai, jaise ki mere didi ke saath 2018 december me hua tha.

Mere didi ko ek din SBI bank se call ata hai aur bank manager kahte hai apka ATM expire hone wale hai isko badal lijiye nhi to apka sara amount ap kabhi nikal nhi payenge. Mere didi kahtey hai thik hai sir par iske liye mai kya karna hoga, Bank manager kahtey hai hum apko naya ATM Card provide karenge, apka account confirmation k liye ek otp ayega wo mujhe batana, fir didi ne bank manager ko OTP de diya. turant didi ke account se Rs.50,000 deduction ho gaya, didi ne turant mujhe call kiya, jab ki mai ICICI me kam karta tha mujhe didi ne call kiya aur ye ghatana ke bare me bataya, maine turant us bank manager ko call kiya jaise mere unse baat hua mujhe pata chal gaya ye koi bank manager nhi hai, maine didi ko iske bare me bata diya, didi ne to bank walo se baat kiya,

Magar ap sochiye ek otp se agar bank khali ho sakta hai to anjan bank ke link se kitna nuksaan ho sakte hai.

Ab baat aati agar apko mail aati hai out side from kotak mahindra bank to kya kare?

Sabse pahle to jo bhi mail aye bank se ap unka email id check kijiye bank ka mail id hai ya kisi our ka, yadi example: Kotak Mahindra bank ka customer hai aur apko dusre kisi bank se mail ata hai to us mail ko kabhi open hi na kare sidha delete kar de. anjan bank ke mail id ko kabhi response na de.

SABHDHAN RAHE SURAKSHIT RAHE...