making a email server illegal when registering

[sherykah]

I've been looking and maybe I'm wording it wrong. I have a spammer who is using the same date of birth and most of the email addresses are for the same email server. I've added some of the usernames into illegal names and that's kept the spammer from using the same names again. Now I've added Admin moderation for new users and that's adding to our duties.

I'm need a modification that will give me the option to make various email servers illegal when registering.