I'm replacing a BT hub with a dedicated PC running OPNSense (a fork of pfsense). I've set up quite a few of these on non BT customers connections and had no problems.
I get everything to connect, using an HG612 modem with a PPPoE connection set up on the OPNSense box. It gets internet and everything seemed to work correctly. However, when I opened Outlook, I received a message from the exchange email set up on it that is the similar to the one described here https://support.microsoft.com/en-gb/help/2772058/the-name-on-the-security-certificate-is-invalid-or-...
Except the last line of text says the problem lies with Cloudflare rejecting the certificate. The OPNSense box is not configured to use Cloudflare for DNS. I asked the provider of the exchange email and they said they could not help. I am wondering if I need any particular DNS setting applied at the PPPoE connection.
I tried adding a new email address and the same message appeared rejecting the autodiscover info because of Cloudflare. It happens on every computer connected to the network when the OPNSense box is used.
Can anyone shed any light on this?