postfix
I’ve blogged about using OpenDKIM with Postfix, having myself run the two together for a quite a number of years now. I’ve set up enough servers from scratch to have compiled my own setup guide. You’d find it cryptic and confusing, so I won’t share it. But what I can share instead is this wonderful guide from EasyDMARC that explains how to configure OpenDKIM to add DKIM support to your Postfix install. I’m so glad they put this all together, and if you’re the right type of email nerd, or want to become one, this is something that you will want to bookmark. Read it here.
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…