HTTP Status Code 400 Error Codes (error property):

InvalidPageNumber - An invalid page number was provided. Valid page numbers are > 0.

InvalidPageSize - An invalid page size was provided. Valid page sizes are > 0.

InvalidFolderId - An invalid folder id was provided. Valid folder ids are > 0.

Note: If the UnreadOnly=true query string parameter is provided, only inbox folder types can be provided.

HTTP Status Code 401 Error Codes (error property):

Unauthorized - An Authorization token was not provided and is required.

AccessTokenInvalid - The access token is expired or invalid.