Postfix install instructions not quite accurate enough?

I've just spent all night trying to install SquirrelMail 1.4.2 and Postfix so i can host virtual domains. After I finally put the SquirrelMail folder into /Library/WebServer/Documents it finally worked, which made me whoop with joy. But trying to install Postfix requires me to do things that no longer seem to be in the instructions at https://www.afp548.com/Articles/mail/postfix.html. For example: -- The line numbers of the main.cf file, which is now a year's worth of revisions older, doesn't correspond with the examples in the article. What exactly should I be uncommenting? -- There is no Sendmail option in the pop-up menu in the Protocols tab in Configure Mail Service... (For that matter, there is no "Server Admin" application now; it's "Server Settings," I believe.) Naturally, now I can't send email, and my achievement with SquirrelMail is moot. I just want to host multiple domains on one server box, and have the email for joe@domain1.com go to joe1, and the email for joe@domain2.com go to joe2. Does it have to be this hard?