Connecting OpenDKIM and Milter configuration on Plesk Obsidian

For the last few days, I couldn't get any external e-mail to verify my DKIM. It sent e-mails and resolved DMARC and SPF just fine. But I literally just FINALLY got it, and since I've come across many others distributed across several forums who've run into this problem, here's everything. It seems that some people have just gotten sick of trying to figure out the answer, and so they ended up installing something different or tried to redo everything.

TL;DR:

The main...

Connecting OpenDKIM and Milter configuration on Plesk Obsidian