Please follow the steps to configure outlook 2016 using IMAP.
Step 1: Open Outlook on your computer and click File option. Then click Add account to setup a new account.
Step 2: Type your email address for which you want to configure outlook. Then click Connect.
Step 3: Choose the account type.
Step 4: It will automatically detect the server setting. If not, then follow the settings as below(Incoming and outgoing mail server should be mail.yourdomainname). Then Click Next to continue.
Step 5: Enter your username and password of email address. Then click OK to complete setup.
Step 6: Once the email account is setup, you need to add some additional settings. Open your outlook and click File.
Step 7: Then click Account settings.
Step 8: Select the email account which you configured and click Change.
Step 9: Check the mail settings, which should be as per the screenshot(Incoming and outgoing mail server is mail.yourdomainname). Once done, click More settings.
Step 10: Click on Advanced tab. Then set the Root folder path as INBOX. Click OK to save.
Then click Next to continue.
Step 11: Outlook will test the incoming and outgoing server settings by sending test email. Click Close when the both the status shows as Completed.
Step 12: Click Finish to Continue. Now you can check all the mails.