code: private int lengthOfTypePrefix(int type) {
          int length;
          switch (type) {
              case EmailRecipientUtils.BCC:
                  length = 4;
                  break;
              case EmailRecipientUtils.CC:
                  length = 3;
                  break;
              case EmailRecipientUtils.TO:
                  length = 0;
                  break;
              default:
                  throw new IllegalArgumentException("Unknown type prefix: " + type);
          }
          return length;
      }
docs: Mind: Include ':' suffix, e.g. for "bcc:<email address>" it is "bcc" + ":", i.e. 3 + 1 = 4