Spam Resource: OpenDKIM and Postfix: Signing DKIM for multiple domains

Al Iverson just shared a new interesting post on Spam Resource:

How do I use OpenDKIM with multiple domain names on a single postfix server? That’s a question I myself had when I first set up my current VPS to host my current email system. So I searched around a bit. I found this guide, but it’s kind of a pain in the rear. Too much heavy lifting.So I tried this instead. It’s a bit of a hacker trick nobody seems to mention online: In your opendkim.conf file, where you specify the domain, you can just include multiple domains here, separated by commas.Instead ofdomain example.comJust putdomain example.com,example.org,mydomain3.comIn your opendkim.conf file.Upside: Super easy.Downside: All domains have to share the same DKIM key, because there’s only one DKIM key setting in opendkim.conf.It works fine. Though you specify the domain name when creating a DKIM key, there’s nothing in the key that is actually domain-specific. At scale, this is insecure. At the hobbyist level, where…

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