Proxy settings to only allow access to exchange server

I have a client who wants his employees to be able to use Outlook 365, but not be able to surf the web.  Based on knowledge from other Microsoft sites, I have done the following (Windows 10):

Control Panel>internet options>connections>LAN Settings

Checked the boxes for "Proxy server" and "Bypass Proxy server for local addresses"

Entered Address 127.0.0.1, Port: 80, then clicked "Advanced."  In the Exceptions box, I entered the following addresses to be whitelisted:

outlook.office.com;outlook.office365.com;smtp.office365.com;r1.res.office365.com;r3.res.office365.com;r4.res.office365.com;*.outlook.office.com;*.outlook.com;attachments.office.net;*.protection.outlook.com;*.mail.protection.outlook.com;*.measure.office.com;login.microsoftonline.com

Now, when the Outlook app runs, it connect to the exchange server and works normally, but no other internet access is allowed.

To keep the employees from tampering with the proxy settings, I changed some of local and domain (everybody is on the same domain) group policies to disable changing the proxy settings locally.

Here's the problem.  It would work fine for a day or two, then suddenly Outlook would stop connecting with the exchange server.  The only way to reconnect was to change all the group policies back, turn the proxy settings off and back on again.  Then I would have to reset all the group policies.  I'm getting sick of doing this every few days.  

Can anybody tell me why this stops working after a while?  Is there something else I can do to make sure it keeps working forever?

Or is there a service that needs restarting to get the connection going again without having to disable/enable the group policies over and over?

Answer
Answer

Hi Wallsguy

Thanks for posting detailed information about your concern here. Based on your description, I have done many researches and I found the reason why you need to refresh your proxy settings and Group Policies might be amount of the proxies you have only support to handle your daily requirement, when the internet accesses of your users become more and more, your proxy servers cannot support to handle the additional load anymore, besides, proxies are not usually designed for persistent connections and your web proxy might also not sized for additional load of Office 365, under the circumstance, they may become a bottleneck. Therefore, we don’t recommend use proxy with Office 365, and there is no way to make sure proxies keep working forever. For detailed instructions, please refer to: https://docs.microsoft.com/en-us/archive/blogs/fasttracktips/why-we-recommend-not-using-proxy-with-office-365  

Best Regards,

Betty

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Last updated May 21, 2020 Views 806 Applies to: