Here is an example of the content of your email message:
Dear .....,
I'm now an online business owner. I'm very glad if you could visit my online superstore.
Find interesting items and services that you like here. Use this TC's Gift Card as a discount voucher.
(Redemption Code: XXXXXXXXXXXX)
However redeeming soon, I'll give it to someone else if you do not use it within 3 months.