Hello. There is:

роутер_adsl: 192.168.1.1 255.255.255.0 dhcp 192.168.1.100-200 wan_adsl 83.174.216.111 gateway 83.174.192.36 роутер_3g: 192.168.1.2 255.255.255.0 dhcp - false 3g - 10.11.12.10

you need to register routes for all machines on the network so that only e-mail traffic is sent to 3G. I admit the change in the settings of each computer.

  • If you have client computers under linux, then it is easy, mark the necessary iptables traffic, wrap it in the desired ip rule routing table. If Windows, then I'm afraid you have a problem ... It's easier to redo the firmware on one of the routers on some openWrt and there it is to solve with link tools. - Mike
  • as an option, I can raise a server with several cards on Linux, besides, I need to organize how to monitor traffic on the network and block it. I have in vosnovnom windows - shaman888
  • Well, there everything is quite simple habrahabr.ru/post/108690 especially pay attention to the section on using iptables packet marking. will need to mark all ports used by mail - Mike

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