I want to block all outgoing emails except to few whitelisted domains. what are the best ways to go about it?

Can I put an intermediate Intranet server which will do filtering based on whitelist and forward requests to actual SMTP server if its allowed?

update: this one is similar but can't figure out actual details. How to properly filter outgoing e-mail?

this looks interesting: https://serverfault.com/a/122772

Update: is it possible to forward same user credentials from relay to actual SMTP server?

  • Your question lacks information. First off, how is your setup even laid out? What software is in use, and what specific configuration have you tried and failed? – Felix Frank Jul 22 '14 at 15:30
  • I dont know which setup you are talking about, it is just one SMTP mail server (came with website server) hosted on HostGator which is being used by small no of people to send emails using Thunderbird/Outlook. – noblocker Jul 22 '14 at 15:36
  • Well this is a site about server operation. For questions regarding you mail client, you should try at SuperUser. – Felix Frank Jul 22 '14 at 15:39
  • Please either flesh out some more details here, or mark this one as answered and put your new scenario into a separate question - again, with more detail. – mfinni Jul 28 '14 at 14:17

Yes. Yes you can - or at least someone can. With the lack of detailed information about your existing setup, that's the most detailed answer I can give you.

/Edit : The only thing you set in the local email client is which SMTP server to send mail through. Create your hypothetical new server and configure your clients to use it. Safelist/blocklist is all done on your new server.

/Edit again, based on your new question. is it possible to forward same user credentials from relay to actual SMTP server?

Could you please describe more fully the problem you're trying to solve, and the constraints you're working under? You haven't even bothered to tell us what MTA you're using or planning to use, and what type of authentication.

  • Thanks for your prompt response. So I've a HostGator hosted smtp server which sends all outgoing emails (very simple setup). So in local email client, I want to put some other SMTP server details which would check if its allowed. If yes, it would contact to actual SMTP server. Is there anything specific you are looking for? – noblocker Jul 22 '14 at 15:14
  • I've edited my answer to address your new information. – mfinni Jul 22 '14 at 16:12

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