I've also seen a Spanish site with this, but as far as I know it has only been accepted by Austrian and German authorities (and challenged recently by some courts).
In the Spanish-speaking world you can find the endings -e, -@, and -x. Depending on the area/organization one or other can be used (also, differing ways of pronouncing them; I'm a native and barely have heard any one pronounce the -e versions ever).
I've also seen a Spanish site with this, but as far as I know it has only been accepted by Austrian and German authorities (and challenged recently by some courts).