Using the Chilkat IMAP component/library, it is possible to authenticate using OAUTH via the SendRawCommand method. Instead of calling the imap.Login method, you would instead call imap.SendRawCommand as shown here:
string response = imap.SendRawCommand("AUTHENTICATE XOAUTH <base64_data>");
Your application will need to compute the OAUTH base64 string. Chilkat does not implement that computations required for generating the OAUTH data.