I received a report from a user using cricket wireless who was unable to access raspbian.org services (which are hosted on 22.214.171.124 and 126.96.36.199
I have checked they can reach a non 5.x.x.x bytemark IP so they appear to be blocking access to that IP range. I am guessing this is because until recently 5.x.x.x was regarded as a bogon and was widely abused by VPN software.
Has anyone else here encountered similar problems? does anyone have any advice for how to approach such ISPs in a way that gives the greatest chance of getting the block removed?