Ubuntu 16.04 server --- Contacting host: elpa.gnu.org:80 when package-refresh-contents

[izzy . yichao . cai]

Hi folks,

I have tried to install elpy in emacs (24.5.1) on my server which is running 
Ubuntu 16.04.

When I run M-x package-refresh-contents, emacs successfully connected to 
stable.melpa.org:443. 
After that, it was hanged on "Contacting host: elpa.gnu.org:80". I am pretty 
sure that I am not behind proxy. 

Then I tried to ping this host and this is what I got:
me@server:~$ ping elpa.gnu.org:80
ping: unknown host elpa.gnu.org:80

However, pinging other websites is normal. I also tried to access this 
(elpa.gnu.org:80) on my local computer and it is accessible.

Does anyone get a hint of what is going on? Thank you so much!


Best regards,
Yichao