The Dispatch

Last updated: 2026-07-31

The Dispatch is a private Flask web application I built to handle all outbound and inbound communication for this site — without exposing my email address publicly, without handing my subscriber list to a newsletter platform, and without any tracking whatsoever.

It lives on PythonAnywhere, separate from the Cockpit. The composing-and-sending side is private; the pieces you touch as a reader — the signup forms, the unsubscribe and preferences links — are public. This page is the technical manual.

Why It Exists

Three things prompted it.

First, I didn’t want my email address on the open web. A contact form is the obvious solution, but most contact form services are either overkill, require accounts, or route your mail through their infrastructure. I wanted something mine.

Second, I wanted to let people sign up for updates when I ship something new — without Mailchimp, without Substack, without handing anyone’s email address to a platform I don’t control.

Third, once you have a subscriber list, you need a way to actually send to it. So I built that too.

The result is one Flask app that quietly does all of it.

What It Does

Contact Form

The contact page on this site submits to a /contact endpoint on The Dispatch. The app validates the fields, composes an email with a Reply-To header set to the sender’s address, and forwards it to my inbox. No data is stored. No copy is kept. It arrives like a normal email and I reply like a normal person.

Update Signups

The signup forms around the site — the Signal List for the workshop, and the notify form on each Tidy app page — let you subscribe to just the things you actually care about. Under the hood these are interest segments: you land in the one you signed up from, and you’re only ever emailed about that.

I tried the opposite first — one undifferentiated list, no channels, no decision at signup. Simpler to build, but wrong in practice: someone who wants to know when one specific app ships doesn’t want everything else too. So segmentation came back — but built so it maintains itself. New signups route to the right segment automatically from the page they came from, I never sort anyone by hand, and you can adjust your own interests any time (see below).

Submissions hit a /subscribe endpoint. The app validates the email and writes the entry to a flat JSON file on the server. Re-subscribing merges your interests rather than duplicating you. No database. No third party holding the list. Just a JSON file I own.

A private, double-locked /send route serves a Markdown composer. HTTP Basic Auth is the first lock — the browser prompts for credentials before the page loads. A second send password is required before anything goes out.

I pick a segment to send to — a specific app, everyone on the whole-family list, or the general workshop list — write in Markdown, and hit Preview. It renders exactly what recipients will see, with a live count of who’s in that segment. Confirm sends each person their own personalized copy, with manage-preferences and unsubscribe links in the footer.

The same private area has a subscriber view (who’s on the list and what they’re interested in, with the ability to add or edit people by hand), a history of everything that’s gone out, and a suppressed list — more on that next.

Keeping the List Clean

Sending real email means dealing with bounces and spam complaints, or your deliverability quietly rots. My email provider tells The Dispatch about these through a signed webhook: a hard bounce or a complaint automatically removes that address and adds it to a suppression list, so it’s never emailed — or accidentally re-added — again. Temporary, soft bounces are left alone.

Every message also carries a proper one-click unsubscribe — the kind Gmail and Apple Mail render as a button — handled by an /unsubscribe route that just removes you. No login. The link is the key.

Managing Your Own Subscription

Every email has a Manage preferences link in the footer. It opens a small page — signed with a token unique to your address, so it only ever touches your subscription — where you can check or uncheck which things you hear about, or leave entirely. No account, no password, no me in the middle.

How It’s Built

Backend: Python, using the Flask framework. Hosted on PythonAnywhere on a separate web app from the Cockpit — different concerns, different deployments. The source is version-controlled (it used to live only on the server).

Email: Sent through Resend’s HTTPS API. I moved off Fastmail SMTP in July 2026 — same sending domain, better deliverability, and the webhook that tells me about bounces and complaints. Resend delivers the mail; it never holds my list. Every message is multipart (HTML plus a plain-text alternative), with proper List-Unsubscribe and one-click headers and a per-recipient Message-ID. The sending domain is verified with DKIM and SPF, and mail comes from my own address.

Subscriber storage: Flat JSON files at fixed paths on the server — the subscriber list, a send log, and the suppression list. Each subscriber entry holds an email, the interest segments they’re in, and created/updated timestamps. Simple enough to read, edit, or back up by hand.

Segments: The whole interest taxonomy lives in one small list in the code. The composer, the counts, and the preferences page all read from it — so adding a new thing to subscribe to is a one-line change, and nothing gets managed by hand.

Markdown rendering: The Python-Markdown library converts message text to HTML before it goes into the email template. The extra and nl2br extensions are enabled — tables, fenced code blocks, and single line breaks work as expected.

Authentication: Two layers on the send-and-admin interface — HTTP Basic Auth at the route level, plus a second application-level send password before anything goes out. The Resend webhook is verified against a signing secret. The preferences links are HMAC-signed per address, so a link only ever manages the address it was minted for.

CORS: The /subscribe and /contact endpoints include Access-Control-Allow-Origin headers locked to aaronaiken.me. Requests from any other origin are rejected before they reach the Flask logic.

Environment variables: All credentials — the Resend API key, the webhook signing secret, the send passwords, the file paths — are set in the WSGI configuration as environment variables. Nothing sensitive lives in application code.

The Email Template

Outbound emails use a minimal HTML template — Georgia serif, warm off-white background, readable at any size. No tracking pixels. No web fonts loaded from external servers. No open or click tracking of any kind.

Each email includes a plain text alternative for clients that prefer it, and a footer with two per-recipient links: Manage preferences and Unsubscribe. Both are keyed to your address alone; clicking unsubscribe removes you from the JSON file immediately and returns a plain confirmation page.

The Stack

Python — core language
Flask — web framework
Python-Markdown — Markdown to HTML rendering
Resend — email delivery (HTTPS API), from a verified custom domain
PythonAnywhere — hosting
JSON — subscriber, send-log, and suppression storage

What It Is Not

The Dispatch is not an email marketing platform. It has no open rate tracking, no click analytics, no A/B testing, no drip sequences, no automations. It sends a message to people who asked to hear from me, and that is all.

What it does now have — after starting deliberately spartan — is the plumbing that keeps a real list healthy: interest segments so people only get what they asked for, bounce and complaint handling so I don’t email dead or annoyed addresses, and a self-service preferences page so you’re never stuck writing to me to change your mind. That’s about as far as it goes, and about as far as it needs to.

The Dispatch is one part of a broader IndieWeb philosophy on this site — own your content, own your infrastructure, don’t outsource the relationship with your readers to a platform. The subscriber list is a text file. The emails come from my domain. A delivery service carries the mail, but the list, the writing, and the relationship stay mine.