They never refer to you by your real name only by your email address or use phrases like my dear friend, dear client etc.
I was scammed once when was selling my car. I advertised it on pistonheads and an hour later I got email saying that there is a problem with my advert. I used the link to the website they sent and once I put my details the browser went blank thats when I realised that somethings wrong. Checked the email header and it wasn't geniue pistonheads. I quickly changed my password.
On this webiste https://haveibeenpwned.com you can check if your details have been compromised.
My was stolen from myfitnesspal few years ago and that time I was mostly using the same password everywhere but since then I always use different for each account.