The issue is not to do with an individual PC or operatiing system. We are a WISP and have our own IP issued by AFRNIC. We realised that blocks of our IP's cannot access microsoft.com. Error displayed is "Internet explorer cannot display webpage" we have done a number of things internally to make sure all is fine. we can access office.microsoft.com. All other Internet sites we access are all fine and in general no complaints from customers Secondary, carrier working fine - using different IP's (trheir IP's) each time we try any IP's in the range of 41.77.168.0 /21 we have experience the problem hence the conclusion. We have seached and checked blacklisting sites, and have delisted in the few places we where listed Does Microsoft as company filter IP blocks? If yes have we been denied access?

try to run an nslookup for microsoft.com and see if you can resolve the IP to the domain name.