code: public Message waitFor(String server, SearchCriteria criteria) throws IOException, MailosaurException {
      	HashMap<String, String> query = new HashMap<String, String>();
      	query.put("server", server);
      	return client.request("POST", "api/messages/await", criteria, query).parseAs(Message.class);
      }
docs: Wait for a specific message.
  Returns as soon as an message matching the specified search criteria is found.
  
  @param server The identifier of the server hosting the message.
  @param criteria The search criteria to use in order to find a match.
  @throws MailosaurException thrown if the request is rejected by server
  @throws IOException
  @return the Message object if successful.