How does one ensure one buys an authentic Xiaomi?
Stay away from online marketplaces that have low barrier of entry
Scammers want quick profit. They won't do things that take time and effort, which is why they're attracted to websites that make it easy to sell stuff.
Contrast this to legitimate online stores: they're usually set up the hard way. For example ShopJoy's website shows a green padlock in the address bar (this means that your safety is protected) and to earn this padlock, ShopJoy had to prove itself as a legitimate Australian business to an external human verifier (GeoTrust).
|Green padlock verifies ShopJoy as an Australian business|
Not only that, we put in the effort to help people research their phones by posting pictures, videos, and reviews, like this Xiaomi Redmi Note 2 product page, for instance. We even lend devices to tech magazines for hands-on review (example 1, example 2). The distance we go in setting up our online store is a sign that we're the real deal.
If the price is too good to be true, it probably is
There are many kinds of costs involved in getting a phone to you. There's shipping cost, currency conversion fee, PayPal/credit card processing fee, eBay commission, etc. If a seller quotes an unbelievably low price, run as fast as you can.
Verify your IMEI and Serial Number
You can check your device authenticity by entering your phone's IMEI and serial number into this online checker tool on the official Xiaomi website.
Check your phone with the Mi Verification app
Alternatively, you can run the Mi Verification app (from the official Xiaomi website) on your phone to check if it's original.
2. Find the downloaded APK on your phone and tap it to install
3. Run the Mi Verification app from your Xiaomi phone once installed
4. The app asks you to scan a QR code on https://jd.mi.com/ , do so
5. The app runs tests and sends results to https://jd.mi.com/
6. Once the tests are finished you can see the outcome on https://jd.mi.com/ . The app itself will not tell you if the phone is genuine, only Xiaomi's official website will.