>> You are absolutely correct, it's 7.27 (on Ubuntu) that works. On Windows,
>> the most recent working version I've managed to find was 7.19.5 . If I could
>> find Windows binaries for 7.27 or 7.28 I'd test them but I can't even
>> find 7.29 (the version I was using) anymore.
>
> Windows binaries are available directly from the curl website for 7.24.0 through the current version 7.32.0
>
> For 7.24.0 and 7.25.0 start at http://curl.haxx.se/gknw.net/win32/
>
> For 7.26.0 onwards start at http://curl.haxx.se/gknw.net/ and follow the path for the version you want (example: http://curl.haxx.se/gknw.net/7.29.0/dist-w32/ for 7.29.0 on 32-bit Windows)

 Excellent, I can now confirm that
curl-7.28.1-rtmp-ssh2-ssl-sspi-zlib-idn-static-bin-w32\curl-7.28.1-rtmp-ssh2-ssl-sspi-zlib-idn-static-bin-w32
curl-7.27.0-rtmp-ssh2-ssl-sspi-zlib-idn-static-bin-w32\curl-7.27.0-rtmp-ssh2-ssl-sspi-zlib-idn-static-bin-w32

Both work.

I tried this one as well :
curl-7.29.0-rtmp-ssh2-ssl-sspi-zlib-idn-static-bin-w32\curl-7.29.0-rtmp-ssh2-ssl-sspi-zlib-idn-static-bin-w32

It doesn't work. So it's really starting from 7.29 that the proxy doesn't work anymore.

I attached a logfile of my tests, as you can see it mostly works (the 503 errors are caused by overloading of the proxy I assume), but as soon as I use >7.29 I get curl error 55.

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