This guide assumes email design and accessibility is already deployed and passing. It covers what breaks at scale and how mature teams operate it.
Edge cases that break a working setup#
- Text embedded in images with no alt.
- Tiny grey text on light backgrounds.
- 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#
- Use a single-column layout that reflows on mobile.
- Set alt text on every meaningful image and empty alt on decorative ones.
- Maintain 4.5:1 contrast and at least 16px body text.
- Include a plain-text alternative and test in dark mode.
Frequently asked questions#
Does dark mode change email colors?
Some clients invert or adjust colors. Test in Gmail, Outlook, and Apple Mail dark modes and use transparent PNGs where possible.