Thanks Amos for the details - I'll give Debian 8 with 3.3.8 a try, as soon as I'm less busy. The support team of the site confirmed me that they use a *non-transparent* proxy. They further told me that they think my proxy had problems with https as their login uses it. Generally, my proxy has no problems with HTTPS connections - HTTPS is being bypassed and so far there weren't problems with it. If you open their portal page in your web browser, it is *not* HTTPS. If you connect without proxy or with non-transparent proxy, the login works and afterwards the page is still *not* HTTPS. So, if just the credentials are being transferred in HTTPS, my assumption would be that some kind of redirection function cannot handle this HTTP/HTTPS-mixture. The following are my IPTABLES rules: Next, the squid.conf: -- View this message in context: http://squid-web-proxy-cache.1019090.n4.nabble.com/Login-on-WWW-page-fails-without-proxy-there-s-no-problem-tp4662055p4662091.html Sent from the Squid - Users mailing list archive at Nabble.com.