Autoreply with coupon

Is there a way to do this.

I want to give of my customers a unique coupon code for a discount for their next purchase. It will be right after their order is complete. Is there a way to do this by e-mailing them?

I also would love to have this option. I asked the forum before, but if I remember right I never got an answer. If anyone can help with this it would be great.