"Illegal" email adress problem

Hi, I didn’t really know where I could post for this trouble but when I tried to change my email adress on my Forum profile it said that I have entered “an illegal email” but this email adress is linked on my Xbox Live Gamertag. Did someone encountered the same problem?
I think it’s not working because there is a "" juste before the “@”. Here is an example: masterchief@halo.com

Thanks.