In an environment containing machines running Windows XP, users may have had difficulties accessing LondonMail when using certain browsers. This issue is related to the blog post below regarding access to secure sites using Windows XP.
In order to grant access to LGfL-supported Microsoft services such as LondonMail, the relevant WebScreen 2.0 filtering policies need to have the Microsoft IP ranges added to the Allowed URL and keyword lists in those policies.
It is important to note that if you have previously allowed the category “Host is an IP” in your policies to overcome problems with accessing LondonMail, then you may wish to consider blocking this category once more to ensure maximum control of access to sites which may be accessed via IP addresses rather than more conventional URLs.
For full details and a list of the required IP ranges please see the WebScreen 2.0 FAQs section found in the Support Site User Guide.