The MAPI classes are used to load Outlook Mapi Messags, saved as .MSG files and provide complete facility to manipulate MAPI properties. From your query, we assumed that you want to retrieve messages from Exchange server in MAPI which is not possible at the moment and we shared information about it’s implementation ticket with you.
You can use the MapiMessage class to read and manipulate Outlook MSG files. You can read and set MapiProperites and work with Named Properties as well. Please let us know if we can be of additional help to you in this regard.