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I’ve been trying to focus on Run Your Own Mail Server throughout October, and making some progress.

Greylisting is a divisive technique. The first time a site mails your server, greylisting delays messages from ten minutes to a couple hours. If people in your organization insist that email is instantaneous despite all evidence to the contrary, that’s a problem. If some web site uses email to send authentication codes that are valid for only ten minutes, that’s an problem. (The problem is that the web site is delivering ephemeral data via an unsuitable protocol but still, you must cope with it.) Some domains use large server farms of MTAs, and resend attempts almost never come from the same IP address. That’s definitely a problem.

One fun thing about greylisting is that you might accidentally deploy it. Postscreen’s deep inspection functions are not deliberate greylisting, but the effects are indistinguishable from greylisting.

I’m still offering sponsorships for RYOMS. But I’ll be offering them next week also. There’s no rush.

Today we’ve got a chunk of Run Your Own Mail Server.

For many years Jon Postel, the Yoda of the primordial Internet, suggested that software should be strict in what it sends but generous in what it accepts. When you wrote an SMTP client you should make it adhere to the standards, but your SMTP server should accept that other people would screw up. In other words: accept the foibles of others.

Spammers’ goal is to deliver the most junk in a minimum of time. Accepting the foibles of others offers spammers a whole bunch of latitude. Spambots implement a stripped-down SMTP that works on most servers. Accepting only clients that rigorously adhere to the protocol definition blocks those spambots. A trickier spambot might implement the beginning part of the protocol correctly, but try to abuse it later. You can check for those violations as well, but those tests might be more intrusive and force legitimate senders to resend their messages.

Before running your own mail server, you should probably read a few of my other tech books. Or skip the whole thing and take up crime. One of them.

In recent years I’ve discovered a talent for Christmas tales. No, not happy cheerful Christmas tales. The other kind. My story The Last Multivariable Differential Christmas is part of WMG’s Holiday Spectacular. Here’s one minute from it.

Bill and Rosie and I were cramming for our multivariable differential equations exam. Of the fifteen students who couldn’t afford tutors, they were the ones who didn’t treat me like a dangerous freak. Doctor Valencia, the math department’s chief bastard, wrote the official textbook to be as impenetrable as the class.

I don’t mind tough programs. I’ve taken a whole bunch of tough classes, in most departments on this stupid campus. I could finish five degrees in one semester, except they’re all too dangerous.

But the math faculty thought tough meant teach badly. Rich students hired tutors and staggered through. Piece work for a dozen professors and tutoring in chemistry and English and business administration and comp sci got me a room and peanut butter, but I didn’t make near enough to pay extortion to math tutors.

Fieldstone gives you three tries at each class. Then they punt you from the department.

If you want the rest of this, back the Kickstarter now. If you’re not sure, check out the anthologies from past years. You’ll find my work in several of them. Usually ones with titles that don’t mention “sweet,” or “joy,” or “mistletoe.” You know.

Let’s have another snippet of Run Your Own Mail Server.

Text file configuration works great for settings that rarely change. If your mail server is truly only for you, then text files will probably be fine. When you have a larger number of users or a more dynamic environment, however, you need easier management. That means a database. And a front end to manage that database, because routinely running raw SQL commands would require memorizing the database structure and that would consume brain space better utilized for something else. Anything else.

Many folks have written database-driven Postfix management systems. Some of them are even adequate. This book will use PostfixAdmin (https://postfixadmin.github.io/postfixadmin/), but primarily to illustrate database-backed Postfix and Dovecot. We won’t go through the web interface, because web interfaces frequently change and once you’ve managed Postfix via text files your most common question is “where did they hide the option for this setting?”

Running your own mail server requires sysadmin expertise. You should probably read some of my other books before trying it.

Here’s a few words about system upgrades–or, rather, a few words about about system upgrades.

Modern systems administrators have outsourced their memory to online forums and search engines, which worked until illiterate large language models got rebranded as AI and the resulting feral autocomplete engines stuffed your external brain’s technology section with reconstituted search-engine-optimized Scorpion fan fiction. Fortunately for you, so did your boss. You have the option to fall back on the computer’s built-in manual, whereas your boss thinks books like The Seven Highly Effective Cheese Mover Habits contains undying management wisdoms. He doesn’t remember anything from that either, but he keeps it on the back of the loo to present an image to anyone foolish enough to enter his lair. No, don’t touch it, the cheap paper those things are printed on absorb ambience and I should know. But did you consider, possibly, for a moment, working on the legitimate issue underlying your question? No you did not, as evidenced by the fact that whatever circuitous “reasoning” process that led you to write and send this letter betrayed you by permitting you to, once again, touch not just a computer but the Internet.

If this amuses you, check out my collection Letters to ed(1).