RSOCKS is a reverse proxy server for transferring traffic of a specific host through a SOCKS 4/5 proxy. It is useful for using SOCKS 4/5 in applications that don't have SOCKS proxy support.

$ pip install rsocks

Or

$ easy_install rsocks

To upgrade to latest version, you could execute:

$ pip install -U rsocks

• OS Service Templates
• Configuration Snippets
• Software Integration Guides

First, we need to create a config file with following format:

# /path/to/rsocks.toml
[servers.foo]
proxy = "socks4://user:pass@192.168.1.10:1080"
listen_host = "0.0.0.0"
listen_port = 5025
upstream_host = "smtp.example.com"
upstream_port = 25
upstream_ssl = false

There is an example for forwarding SMTP/IMAP of Gmail through a SOCKS5 proxy server:

[servers.imap]
proxy = "socks5://localhost:1080"
listen_port = 5993
upstream_host = "imap.gmail.com"
upstream_port = 993
upstream_ssl = true

[servers.smtp]
proxy = "socks5://localhost:1080"
listen_port = 5465
upstream_host = "smtp.gmail.com"
upstream_port = 465
upstream_ssl = true

Next, we start the rsocks server:

$ rsocks --config=/path/to/rsocks.toml
[14:24:44] rsocks.servers.smtp       Using proxy server socks5://localhost:1080
[14:24:44] rsocks.servers.smtp       Listening 127.0.0.1:5465
[14:24:44] rsocks.servers.imap       Using proxy server socks5://localhost:1080
[14:24:44] rsocks.servers.imap       Listening 127.0.0.1:5993
[14:24:44] rsocks.pool               Prepared "smtp"
[14:24:44] rsocks.pool               Prepared "imap"
[14:24:44] rsocks.servers.smtp       Starting server...
[14:24:44] rsocks.servers.imap       Starting server...

Don't stop it now, open your application (such as Airmail in OS X) and set the server option to local forwarding address:

SMTP: 127.0.0.1:5465 without SSL
IMAP: 127.0.0.1:5993 without SSL

Now the application's traffic will be forwarded through the proxy server (socks5://127.0.0.1:1080).

If you wish to run the rsocks server in background, please check the Platform Service Templates. For example, OS X users can create com.tonyseek.rsocks.plist file in ~/Library/LaunchAgents and load it as a service:

$ nano ~/.rsocks.toml  # create a config file
$ wget https://github.com/tonyseek/rsocks/blob/master/misc/platforms/osx-launchd/com.tonyseek.rsocks.plist \
      -O ~/Library/LaunchAgents/com.tonyseek.rsocks.plist
$ nano ~/Library/LaunchAgents/com.tonyseek.rsocks.plist  # edit the template
$ launchctl load -w ~/Library/LaunchAgents/com.tonyseek.rsocks.plist

There is an example for using API to build a server:

import os

from rsocks.pool import ServerPool
from rsocks.server import ReverseProxyServer

proxy = os.environ.get('SOCKS_PROXY', 'socks5://localhost:1080')
pool = ServerPool()

with pool.new_server(
        name='IMAP',
        server_class=ReverseProxyServer,
        upstream=('imap.gmail.com', 993),
        use_ssl=True) as server:
    server.set_proxy(proxy)
    server.listen(('127.0.0.1', 5993))

with pool.new_server(
        name='SMTP',
        server_class=ReverseProxyServer,
        upstream=('smtp.gmail.com', 465),
        use_ssl=True) as server:
    server.set_proxy(proxy)
    server.listen(('127.0.0.1', 5465))

if __name__ == '__main__':
    pool.loop()