This guide assumes spam filter content triggers is already deployed and passing. It covers what breaks at scale and how mature teams operate it.
Edge cases that break a working setup#
- Image-only emails.
- Tracking links on a shared domain used by spammers.
- Mail forwarded through mailing lists or personal forwarders, which alters headers and content.
- Acquisitions and rebrands that introduce domains nobody audited.
- Vendors silently changing their sending infrastructure.
Operating it as infrastructure#
- Assign an owner for each sending domain and each vendor relationship.
- Put DNS records under version control or a change-review process.
- Alert on authentication pass rate drops and reputation changes, not just outages.
- Run a quarterly audit against the setup steps below.
- Document runbooks for the three most common failures.
Reference: the baseline setup#
- Keep a healthy text-to-image ratio and always include a plain-text part.
- Link to your own domain; avoid shorteners and tracking domains with poor reputation.
- Make link text match the destination.
- Test rendering and spam scores before sending.
Frequently asked questions#
Are spam trigger words still a thing?
Much less than a decade ago. Modern filters are statistical and reputation-weighted. Deceptive intent matters more than any single word.