You can allow your users to import email and contacts from non-Google webmail accounts, such as Yahoo!, Hotmail, or AOL. First, you must enable this feature in your Google Admin console. After that, users will see an extra function in the Accounts tab in Gmail settings. 

You can only enable or disable importing from other webmail hosts for all users in your account. You can’t customize this setting for any sub-organizations you have created.

To enable importing from other webmail hosts:

1. Sign in to the Google Admin console.
2. From the dashboard, go to Apps > G Suite > Gmail > Advanced settings.
3. In the Setup section, check the box next to User email uploads to let users see the option to import mail and contacts from webmail or POP3 accounts, such as Yahoo!, Hotmail, or AOL.Tip: If you don’t see this section, select your account’s top-level organization under Organizations at the top of the page. This feature isn’t available when a sub-organization is selected.
4. Click Save. There might be a delay before changes take effect.
5. Tell your users to go to Gmail > Settings to start the import process. For details, see Import contacts into your Gmail account and Check email from other accounts with Gmail.

To disable importing from other webmail hosts:

To disable importing from other webmail hosts, simply uncheck the box in step 3 and save your changes.