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I am configuring a company private mailman server, where we want people inside the company to be able to subscribe and unsubscribe freely... And block any attempts from anyone outside the company.

Is there some whitelisting/blacklisting/pattern matching capability, to automatically accept subscriptions from within the company and deny from outside?

Sounds like a firewall issue. Run Mailman on a separate port, and block it outside the firewall.

Our primary mailserver is outside the firewall, so if I block all inbound port 25, then my own users can't email the list. Otherwise the firewall would be a good solution.

Now that you mention it, I think there will be some good along these lines. I can configure our firewall to only allow port 25 from a specific IP. And I think I can configure exim to only allow email "From: " a specific domain. It doesn't have to be inside of Mailman, as I was previously thinking.

Then I can configure Mailman as loosey-goosey as possible, and rely on the underlying stuff instead.

Thanks, ttyl...