Hi All,

while ago, i was at customer site configuring their SCCM infrastructure and the Windows Update was failing for almost every single computer with the following log lines

WARNING: Send failed with hr = 80072f78.

WARNING: SendRequest failed with hr = 80072f78. Proxy List used: <10.7.7.247:3128> Bypass List used : <(null)> Auth Schemes used : <Basic;NTLM;>

WARNING: WinHttp: SendRequestUsingProxy failed for <http://UPPERCASEFQDNNAME:8530/selfupdate/wuident.cab>. error 0x80072f78

WARNING: WinHttp: SendRequestToServerForFileInformation MakeRequest failed. error 0x80072f78

WARNING: WinHttp: SendRequestToServerForFileInformation failed with 0x80072f78

WARNING: WinHttp: ShouldFileBeDownloaded failed with 0x80072f78 

after a bit of trobleshooting and searching over the net, I found that the UPPERCASE FQDN was causing the issue, I changed the Intranet name from uppercase to lowercase (SCCM Console->Site Database->Site Management->Site Code->Site Settings->Site Systems->SUP Server->ConfigMgr site system) and forced the client to update policy and tried again. 

at this point, everything worked as it should be.
 
What I learned from this: if there is any Linux proxy/firewall, always use the lowercase FQDN.