Heres my pragmatic approach, where I just want reasonable distinct blah@domain addresses using the allowable characters from the RFC. Addresses must be converted to lowercase beforehand.
public class EmailAddressValidator {
private static final String domainChars = "a-z0-9\\-";
private static final String atomChars = "a-z0-9\\Q!#$%&'*+-/=?^_`{|}~\\E";
private static final String emailRegex = "^" + dot(atomChars) + "@" + dot(domainChars) + "$";
private static final Pattern emailPattern = Pattern.compile(emailRegex);
private static String dot(String chars) {
return "[" + chars + "]+(?:\\.[" + chars + "]+)*";
}
public static boolean isValidEmailAddress(String address) {
return address != null && emailPattern.matcher(address).matches();
}
}