After NMIMS application completion we receive any confirmation mail or not? I have paid but not received any mail or receipt.

you'll get the email a little late, Just check if you are able to download the receipt directly from the nmims website.

I Got A overall score of 212 in nmat. Should I Go for reattempt or is it enough for nmims mumbai? If I go for reattempt what should be the target score to get call from nmims mumbai

Reattempt for sure if targetting NMIMS Mumbai.

I guess 220+ is good enough for Mumbai campus. Why is everyone saying to score 240+ in order to get a call ?