code: public static boolean isValid (@Nullable final String sEmailAddress)
    {
      if (sEmailAddress == null)
        return false;
  
      // Unify (lowercase)
      final String sUnifiedEmail = getUnifiedEmailAddress (sEmailAddress);
  
      // Pattern matching
      return s_aPattern.matcher (sUnifiedEmail).matches ();
    }
docs: Checks if a value is a valid e-mail address according to a certain regular
  expression.
  
  @param sEmailAddress
  The value validation is being performed on. A <code>null</code>
  value is considered invalid.
  @return <code>true</code> if the email address is valid, <code>false</code>
  otherwise.