An annoying problem, remarkably similar to another post re Macs.
One one of 4 devices I was unable to connect to BT Mail, from 4th October onwards.
The device concerned is a Windows 7 laptop. which would not connect via Outlook (2010 and 2013).
After turning the computer system upside down and inside out, flush DNS, changing Bt Mail passwords several times, factory resetting the HH5, BT Mail would not connect. Error message produced by Outlook Repair was along the lines "unable to obtain secure connection to server". The connection is via SSL pop3, ports 995/465.
All other Internet connections on that same laptop were available, however.
The final fix, after 3 days, was to plug in a USB wireless adapter. (even USB devices are no longer considered to be absolutely secure, from recent news). With the USB adaptor I can connect without problems.
What is going on? All other devices - desktop, mobile phone, iPad, iPod are OK.