code: protected IMessagePublication addAsynchronousPublication(MessagePublication publication) {
          try {
              pendingMessages.put(publication);
              return publication.markScheduled();
          } catch (InterruptedException e) {
              handlePublicationError(new InternalPublicationError(e, "Error while adding an asynchronous message publication", publication));
              return publication;
          }
      }
docs: this method queues a message delivery request