is there a way to filter out all the tasks that are created directly as task from within outlook?
Unfortunately, no. You can query them by keywords that's common among the other tasks though (if they had one). As always, you can add a request in the Votebox https://todoist.com/Vote/.
Although, as Clyde mentioned, there is no direct standard way to do this, you could try to search just for the word Outlook as these tasks contain a local URL that starts with outlook://