Symptoms#
- Messages landing in spam despite previously good placement
- Bounces mentioning policy, authentication, or reputation
- Provider dashboards showing a drop in reputation or authentication pass rate
Diagnosis steps#
- Confirm the configuration is live: query DNS from an external resolver and check the sending platform's settings page.
- Send to a seed mailbox and read the full headers, especially Authentication-Results.
- Compare the domains in From, Return-Path, and DKIM d= for alignment.
- Check provider dashboards (Google Postmaster Tools, Microsoft SNDS) for reputation and error rates.
- Review recent changes: new vendors, DNS edits, list imports, volume spikes.
Likely causes#
- Text embedded in images with no alt.
- Tiny grey text on light backgrounds.
Fix and re-verify#
- 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.