Is there a way to limit the list of mailadresses a user can send mail to, to a small whitelist of approved addresses?

The only option I can think of right now is a customized contact form, but I'm looking for a better way that is or can be integrated in an existing mailclient?

closed as too broad by Steffen Ullrich, symcbean, AndrolGenhald, multithr3at3d, Xander Jun 11 '18 at 23:07

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • It is unclear about what kind of setup you are talking. A MTA (which), a firewall or mail gateway, a desktop system, a web mail client, ... ? I propose to close the question as too broad. – Steffen Ullrich Jun 11 '18 at 10:49
  • I agree. I realize that the question is more like a consulting one. And I currently lack trivial knowledge about the SMTP protocol to know it can be configured. I turned to SE because Google let me down, I need to do more research myself to get an answer to my question how a regular user can control the whitelist for outbound email of a second user. Fortunately vidarlo has pointed me towards a solution. – Code4R7 Jun 12 '18 at 18:54

Yes. Set up whatever mail server you use to filter mail based on destination. This is trivial.

For Postfix this is solved with the check recipient access table configuration directive, which lets you configure either a system wide, or per user allowed destinations. For different MTA's there's different options.

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