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SPF: a field note from a hardware store
2 Jul 2025
How a hardware store deals with SPF — and what usually goes wrong.
The problem: a certificate that expires on a Sunday. The SPF check fails for a hardware store.
Instead of migrating SPF all at once, we ran both configurations in parallel for a week. The switch happened on a Wednesday morning — the quietest traffic window.
The vendor portal had silently rotated the key for SPF, but a hardware store was still using the old one. Every outbound message bounced quietly.
When a hardware store moved hosts, the outage was not the new box — it was a certificate that expires on a Sunday. We keep TTL short the week of a move, then raise it once everything is stable.
A static site for a hardware store does not need a CDN, a build pipeline, or a container. It needs correct SPF and a host that stays online.
A form that collects data for a hardware store should say where the message goes. Nine fields and a captcha on a quiet Tuesday will cost you the person who actually wanted to pay.
We hand over a one-page document after every SPF job. It says what was changed, what the login is, and what to check if something feels wrong. a hardware store keeps it in a drawer they actually open.
The most expensive outage for a hardware store was not a hack — it was a certificate that expires on a Sunday. Nobody attacked anything. The config just drifted.
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