When you place your email in a bio, yes it normally happens.  If you want to limit this, you can split your email up and the users who want to send you giftcards will need to put it together for it to work.  Otherwise you can make an image with your email written in it, this way can be more secure for you, but it may still happen.

Sometimes the best way that some models have found is to have a wish list with sites like Amazon, add the voucher to the wish list and add a note with your email address underneath