How to avoid the scam
This is what the message looks like:
The easiest way to spot if it's phoney is the spelling and grammar mistakes - "Enjoy and thanks me later", for example.
If you type the URL http// www.asda.com/mycoupon into your browser or Google it, the page does not exist on ASDA.
If you do click it, it will just take you to the scammer's website.
There seems to be something similar to this every week and this wouldn't happen if people didn't keep falling for it, so make sure you aren't one of them.