What are the two main methods to access Exchange resources using Exchange Web Services (EWS)?

The two main methods are the EWS Managed API and EWS SOAP XML messages. The Managed API provides a .NET or PowerShell wrapper for easier development, while the SOAP XML method allows direct crafting and parsing of SOAP requests and responses. For a deeper dive into SOAP messages, see the Exchange Web Service (EWS) Development Guide 2 – SOAP XML Message.