We want to use Slack Webhook (Outgoing Webhook) with an internal web service.
Our company is behind a firewall, so outside connections must be whitelisted.
It appears that Slack has multiple addresses it will send the API request from, and they don't seem to be documented.
Which IPs/Ports should we open in the firewall (whitelist) in order to allow slack's outgoing webhooks to connect to our internal web service?
An alternative could be using a VPN tunnel service to expose your internal webserver the Internet, e.g. with ngrok. I can confirm it works with Slack (I use it every day for Slack developing) and its also recommended as solution for a local development environment in the Slack tutorials.
来源：https://stackoverflow.com/questions/38759599/slack-webhook-which-ips-should-i-open