wordpress setup behind an authenticated proxy server

First of all I am totally new on WP ?? said that.

I am getting errors such as An unexpected error occurred. Something may be wrong with www.remarpro.com or this server’s configuration. When I try to add new themes or plugins for instance.

First I setup my linux machine where wordpress is installed to go through my corporate proxy.

Then I tried entering the following configuration to the wp-config.php file:

define('WP_PROXY_HOST', 'proxy.company.es');
define('WP_PROXY_PORT', '8080');
define('WP_PROXY_USERNAME', 'myarea\\myusername');
define('WP_PROXY_PASSWORD', 'mypass');
define('WP_PROXY_BYPASS_HOSTS', 'localhost');

I also tried enterig this configuration to the config-mysitename.php file.

I am stuck at this point. I suspect that the problem could be the value (‘myarea\\myusername’) I am giving to WP_PROXY_PASSWORD

I tried all this values:
‘myarea\\myusername’
‘myarea%myusername’
‘myarea\myusername’

any idea what I am doing wrong?

thanks in advance