When investigating an updating issue on your endpoint, if telnet to dci.sophosupd.com on port 443 shows a problem, what is most likely causing this?

When trying to determine the root cause of an updating issue by testing the ability to connect to dci.sophosupd.com on port 443 using telnet, encountering a problem indicates that there may be a blocking mechanism in place. If the Windows client firewall is blocking traffic on this port, it would prevent the endpoint from establishing a secure connection necessary for updates to be downloaded and installed.

Port 443 is typically used for secure web traffic via HTTPS, and firewalls are often configured to restrict or allow traffic based on port numbers. If the firewall settings do not permit outgoing connections on port 443, the connection attempt will fail, thus resulting in an inability to contact the Sophos update server, which is essential for the endpoint to receive the latest updates.

In the context of other possible causes, incorrect proxy settings could lead to issues connecting to the update server, but if telnet fails on port 443, it more strongly suggests that the communications are being blocked at the firewall level rather than misconfigured proxy settings. Similarly, network connection issues might also be a factor, but those would likely affect connectivity to more than one destination, not specifically to the Sophos update server. Outdated software version is not likely to directly affect the ability to