Emacs is able to access the Internet with packages such as url.el or the W3 web browser.
Also, the Emacs Lisp Package Archive is heavily dependent on package url.el.
Now, how do I configure Emacs to use my HTTP proxy to connect to the Internet in general?
Bonus points for any help with ELPA behind a proxy.
This is a bit old, but I had issues connecting as well. One thing I needed to do is add my certificate to the the gnutls-trustfiles in order to connect.
(with-eval-after-load 'gnutls
(add-to-list 'gnutls-trustfiles "path/to/cert.crt"))
(setq url-proxy-services
'(("no_proxy" . "^\\(localhost\\|10\\..*\\|192\\.168\\..*\\)")
("http" . "proxy.com:8080")
("https" . "proxy.com:8080")))