How to monitor the HTTP Alert Action?

Hi, I am trying to send data from Splunk to a Lotus Notes bases Incident Management. This system can recieve events as SOAP messages. So I bulid the required XML structure within the search as an eval command and trigger the HTTP Alert Action. There I put in all nessecary headers and the xml as data. Now I´ve the problem, that no messages reach their destination. How can I troubleshoot this? I transmitted the xml manually with curl. That works. So the xml format is correct and the server is rechable over the network. Somethime I get an errorcode 4 in Splunk Internal index. What is error 4? Thank you.