Hello Antxon,

I was looking into your post and in order to achieve this functionality I can suggest you handle the LostFocus event of the XamNumericEditor and check if the entered value match the email regex pattern like this:

        private void XamNumericEditor_LostFocus(object sender, RoutedEventArgs e)

        {

            string strIn=(sender as XamMaskedEditor).Value.ToString();

            (sender as XamMaskedEditor).IsValueValid= Regex.IsMatch(strIn,

             @"^(?("")("".+?""@)|(([0-9a-zA-Z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9a-zA-Z])@))" +

             @"(?(\[)(\[(\d{1,3}\.){3}\d{1,3}\])|(([0-9a-zA-Z][-\w]*[0-9a-zA-Z]\.)+[a-zA-Z]{2,6}))$");

        }

You can find this possible approach to set an email regex in the following link from msdn with detailed description of the sintaxis:

http://msdn.microsoft.com/en-us/library/01escwtf(v=vs.95).aspx

Please notice that by setting the property IsVlueValid to false the editor itself will show a red border to indicate the incorrect value.

If you need any additional assistance on the matter, please do not hesitate to ask.