I am following along with this Microsoft post to get some code written against our exchange server. My goal was to loop through each contact in a specific folder and write each contact to my sql database. I have a custom property on each contact that is the customers ID number which I want to include in each database record. The question I have is this, am I looking for a specific set GUID that is somewhere to be found on the exchange server for my extended custom property? How do I go about finding that guid?

EDIT: Here is the link because it kept breaking when trying to format lol. https://docs.microsoft.com/en-us/previous-versions/office/developer/exchange-server-2010/dd633697(v%3Dexchg.80)