Give this one a try. I did some minimal validation at this site, but you should double-check and make sure it matches the email addresses you want to limit to.

^[A-Za-z0-9._%+-]+@ourdomain.com$

It looks like the email regular expression is hardcoded into register.aspx. You can clone register.aspx to a custom name (like registerme.aspx), and then add this key to your user.config:

<add key="CustomRegistrationPage" value="/path/to/registerme.aspx"/>

Finally, edit registerme.aspx and change the following validator declaration to use your custom email address regex:

<asp:RegularExpressionValidator ID="EmailRegex" runat="server" ControlToValidate="Email"
Display="None" ValidationExpression="^([0-9a-zA-Z]([-.\w]*[0-9a-zA-Z])*@(([0-9a-zA-Z])+([-\w]*[0-9a-zA-Z])*\.)+[a-zA-Z]{2,9})$"
ValidationGroup="profile"></asp:RegularExpressionValidator>

Be sure to touch web.config after editing user.config, and test thoroughly.

Hope that works for you.

Jamie

Yes, this is now implemented in the source code repository so it will be in the next release. You will be able to add these settings to user.config populated with your regex expression and your error message

<add key="CustomEmailRegex" value=""/>
<add key="CustomEmailRegexWarning" value=""/>

Best,

Joe