Outlook 2016 volume licensed version with Windows Installer (MSI) does not support OAuth.To let your users sync Gmail with third-party mail clients, turn on IMAP in the Admin console by following the steps in Turn POP and IMAP on and off for users. Before you begin: Turn on IMAP in the Admin console In this case, contact support for the third-party mail app.
Important: Your support plan might not include support for third-party products. We recommend using the latest versions of: If you're not sure if your email client supports OAuth, contact tech support or check the help documentation for the client. The latest versions of Outlook, Apple Mail, and Samsung Mail support OAuth. Email clients that use OAuth keep your Gmail account more secure. We recommend you use Gmail only with third-party email clients that support OAuth. OAuth lets apps and websites share your Google account data without requiring your username or password. This article has steps for admins and users to set up Gmail with another mail client. Your users might want to send and receive mail from other email clients, for example Microsoft Outlook or Apple Mail.
