Unable to rewrite a webpage in nginx

worker_processes 1;

worker_rlimit_nofile 30000;

events {

worker_connections 1024;

}

http {

include mime.types;

default_type application/octet-stream;

sendfile on;

keepalive_timeout 65;

server {

listen 80;

server_name 192.168.17.53; #My Nginx Server

rewrite ^/(.*)$ http://mailsvr.parco.net.pk/mail/ permanent;

client_max_body_size 100m;

location /{

 proxy_pass http://mailsvr.parco.net.pk/;# mailserver internal name

proxy_redirect http://mailsvr.parco.net.pk/mailsvr/mail/ http://mailsvr.parco.net.pk/mail/; # redirecting mailserver webpage

proxy_set_header X-Real-IP $remote_addr;

proxy_set_header X-Forwarded-For $remote_addr;

proxy_set_header X-Forwarded-Proto $scheme;

proxy_read_timeout 240;

proxy_buffering off;

}#end location

}#end server

}#end http