Find email-enabled public folders exclusively using "Microsoft.Office.Interop.Outlook"

[temuco]

Is there a way to exclusively identify email-enabled public folders using Microsoft.Office.Interop.Outlook? EWS or PowerShell should not be used. The program should run on the workstation and utilize the installed Outlook. Once I've found an email-enabled public folder, I should list the emails contained within it. So far, I'm encountering difficulties. For instance, I have the following method:

// Recursive method for listing the email addresses of email-enabled public folders
static void ListPublicFolders(Outlook.Folder? folder, string indent)
{
if (folder != null)
{
foreach (object obj in folder.Folders)
{
if (obj is Outlook.Folder)
{
Outlook.Folder? subFolder = obj as Outlook.Folder;

            if (subFolder != null && subFolder.DefaultItemType == Outlook.OlItemType.olMailItem)
            {
                Outlook.MAPIFolder? parentFolder = subFolder.Parent as Outlook.MAPIFolder;
                string              parentName   = parentFolder != null ? parentFolder.Name : "Parent folder not found";

                Console.WriteLine($"{indent}- {subFolder.Name}: {parentName}");

                if (parentFolder != null)
                {
                    Marshal.ReleaseComObject(parentFolder);
                }
            }

            ListPublicFolders(subFolder, indent + "  ");

            if (subFolder != null)
            {
                Marshal.ReleaseComObject(subFolder);
            }
        }
    }
}

}

The query

if (subFolder != null && subFolder.DefaultItemType == Outlook.OlItemType.olMailItem)

fails because subFolder.DefaultItemType returns the value Outlook.OlItemType.olPostItem, even though the public folder was set up as an email-enabled folder in Exchange. Specifically, this is in Microsoft 365. In the Exchange admin center, when creating the folder, I explicitly checked the box for "Email-enabled." This action resulted in two additional options: "Delegation" and "Email properties." In "Email properties," I can specify an alias and a display name. By default, both fields are set to "Orders." Now, I expect the public folder to be email-enabled, with the email address orders@domain.tld. I don't understand why Outlook is treating the folder incorrectly (I can only create posts and not send emails). Perhaps someone can help me figure this out. Thank you and