Health Report
The health report is a practical QA layer for common email problems. It is not a replacement for human review or inbox testing.
What MailMode Checks
MailMode’s Health Report is split into quick signals and deeper diagnostics. It checks the rendered email, inbox preview copy, tracking, accessibility basics, dark mode readiness and selected client risks.
The health report is a practical QA aid. It highlights likely issues, but it does not replace final review or real email-client testing.
Small pills summarise the main risks immediately after preview.
Detailed cards explain rendering, inbox, tracking and client checks.
Warnings appear only when MailMode finds something worth reviewing.
Colours, Icons and Statuses
The report uses the same colour language throughout the app. The colour tells you how urgent the item is before you read the details.
No obvious problem was detected for that check.
Worth reviewing. It may be fine, but email clients can be unpredictable.
Likely needs attention before sending or sharing for approval.
Informational. Usually means there was nothing relevant to check.
Analysis Summary / Quick Scan
The quick scan is the compact row beneath the previews. It keeps the interface light while still surfacing the important checks.
Subject or preheader is missing, too short, too long, duplicated or suspicious.
No missing image alt text was found in the rendered email.
Shows whether UTMs, ESP tracking, click IDs or open pixels were found.
Counts links that MailMode can analyse without following them.
Total warnings and issues from the current report.
Full Health Report
The full report expands the quick scan into detailed cards. These cards are grouped by rendering, email health, tracking and potential issues.
Detailed rendering, tracking, accessibility, and client checks.
Rendered HTML size.
Looks for prefers-color-scheme rules.
Checks mode hints.
Detects data-ogsc and data-ogsb.
Rendering Checks
Rendering checks are static signals from the compiled email HTML. They do not guarantee inbox-perfect behaviour, but they highlight common dark mode and email-client risks.
Green when comfortably below Gmail clipping risk. Warning near roughly 85 KB. Issue above roughly 102 KB.
Checks whether the email includes prefers-color-scheme: dark rules.
Looks for colour scheme hints that tell clients the email supports light and dark rendering.
Checks for supported-color-schemes, a common email dark mode hint.
Detects community-observed Outlook.com and Outlook-on-the-web dark mode hooks such as data-ogsc and data-ogsb. These are not a general signal for every Outlook app. Neutral means they were not found.
Authored vs Forced Dark Mode
Gmail forced-dark protection is reported only for a single exact light only colour-scheme meta declaration. Select Google-hosted or GANGA account type when testing Gmail mobile. Duplicate/invalid declarations are flagged for review. An authored dark theme with this protection can trigger an Apple Mail conflict warning unless a root color-scheme: light dark rule restores support.
The Dark Mode Behaviour card explains whether MailMode found developer-authored dark CSS and how the selected client profile may treat it. Authored CSS is evaluated from real rules in the rendered HTML; a class named dark by itself is not enough.
The compiled email contains a dark/light media rule, a colour-scheme declaration or a relevant Outlook dark selector.
The selected profile may recolour the rendered message independently of authored CSS.
Gmail Web, Gmail Android, Gmail iOS, Outlook Classic, New Outlook/Web, Outlook Mobile and Apple Mail each map to a documented MailMode behaviour model.
Profiles predict common behaviour; they are not live-client screenshots or exact reproductions of unpublished algorithms.
Subject & Inbox Preview
This card checks whether MailMode can detect subject and preheader copy. It is an approximate inbox preview to help spot length and spacing issues; actual inbox display can vary by client and device.
No subject or preheader was detected in this file.
Preheader not detected
HTML <title>, hidden preview text, MJML <mj-title>/<mj-preview>, or React Email <Preview>.
No subject was detected. In a real send, the subject may live outside the HTML, but MailMode cannot verify it unless present.
No hidden preview text was detected near the top of the email.
Very short copy may waste inbox space. Long copy may truncate, especially on mobile.
Repeating the same text wastes the preheader area.
Uses a simple wording and formatting heuristic to flag phrases, excessive punctuation, repeated emojis or all-caps subject lines for human review. It is not a deliverability test or spam-filter prediction.
Tracking Check
The Tracking Check scans links and image tags without making external requests. Tracking links are common in email campaigns; MailMode flags tracking-style links, analytics parameters and redirect patterns so you can review whether they are expected.
0 tracked links detected, 0 untracked links.
No obvious tracking consistency issues were found.
Usually means missing UTMs or open tracking pixels are present and worth reviewing.
Used for incomplete required UTMs, inconsistent UTM values or multiple tracking layers on the same link.
Links with UTMs, ESP click tracking, click IDs, affiliate parameters, CRM IDs or similar.
HTTP/HTTPS links with no detected campaign tracking.
Hidden, 1x1, transparent or tracking-keyword image URLs that may be used for opens.
Potential Issues
Potential issues are the general warning cards shown after rendering checks. If there are no warnings, MailMode shows an All clear card.
No warnings found in the rendered email.
HTML is approaching or over Gmail clipping size.
One or more images are missing alt text.
Script tags were stripped from preview.
Large emails can be clipped by Gmail, hiding content below the cutoff.
Most email clients block scripts. MailMode strips them from previews.
Forms are inconsistently supported in email clients and may fail.
Missing alt text affects screen readers and image-blocked inboxes.
Fixed widths above 640px can cause awkward scaling or clipping on smaller viewports.
Browser MJML cannot fetch included files. Inline included content before previewing.
Extra markup outside the main MJML root is ignored so the email can still compile safely.
Authored dark media CSS was found without a compatible light-and-dark scheme declaration. This matters to supporting clients such as Apple Mail, not Gmail forced dark mode.
A Tailwind dark: class was found in JSX but no compiled dark media rule was present. Export and analyse the real build output.
An explicit transparent or semi-transparent background appears in an Outlook/VML-relevant context.
Personalisation tokens appear inside a fixed-height VML background and could change the required height.
A rounded VML button appears inside a VML background. The narrow combination can be fragile in classic Outlook and after forwarding.
Major table, conditional-comment, style or VML mismatches can cause document-wide rendering failure.
Additional Gmail, Apple Mail or Outlook checks appear when the relevant named profile is selected.
Client Check Warnings
Client profiles add lightweight, client-specific warnings and map the preview to an existing generic mode. These are static predictions, not real inbox screenshots.
Uses an authored/no-change baseline and flags Gmail CSS, clipping and link risks without claiming mobile-style inversion.
Uses partial- and full-invert risk models respectively, with wording that acknowledges unpublished, changing algorithms.
Uses the authored CSS model and checks that dark rules have appropriate colour-scheme opt-in.
Uses the full-invert model and adds Word, MSO, transparency, structural and VML checks.
Uses a partial-invert model and checks relevant Outlook web selectors such as data-ogsc and data-ogsb.
Uses a deliberately low-confidence partial-invert model and keeps mobile behaviour separate from classic Outlook.
How to Use the Report
Start with red issue cards, then review amber warnings. Green cards are useful confirmation, but they do not mean every inbox will be perfect. Avoid uploading or sharing sensitive or confidential content, and remember that shareable previews are temporary public links while active.