Ok, assuming its not enabled, then you can follow this:
https://practical365.com/exchange-server/how-to-configure-exchange-server-2010-outlook-anywhere/
https://learn.microsoft.com/en-us/powershell/module/exchange/enable-outlookanywhere?view=exchange-ps
Remote outlook clients may have to create new profiles to use Outlook Anywhere. Outlook does not behave as it should always. But once setup, they should be good to go.
Ensure you understand the certificate and firewall requirements
Also, DO NOT set the Outlook Anywhere namespace the same as the CAS Array FQDN. Make it unique for the day when you upgrade to a supported version of Exchange.
https://techcommunity.microsoft.com/t5/exchange-team-blog/ambiguous-urls-and-their-effect-on-exchange-2010-to-exchange/ba-p/593809