Fix Custom Font Fallback Overrides in iOS Mail (Apple) — Klaviyo Guide for Client Rendering Engine Anomalies
Email client rendering variations are caused by differences in parser engines. Legacy Outlook engines ignore modern block models, forcing layouts to stack vertically. Below is the targeted integration guide to fix Custom Font Fallback Overrides inside iOS Mail (Apple) templates when using Klaviyo.
Technical Breakdown
iOS Mail supports web typography but strips imported fonts if stylesheet links are blocked by strict privacy filters.
Klaviyo Behaviors
Klaviyo's drag-and-drop template parser automatically wraps all user-defined block sections in proprietary 'kl-part' class selectors. When rendering templates inside Microsoft Word engines (Outlook 2007-2021), Klaviyo's nested flex fallback blocks can cause structural tables to collapse or shift columns. You must use explicit table widths to override Klaviyo's styling wraps. Test layout code regressions side-by-side using the Campaign Diff Comparator before pushing visual style changes to your production templates.
Remediation Code Block
To prevent Outlook's Times New Roman fallback override, wrap your custom font declarations inside an @media block that Outlook ignores, or use MSO conditional statements to override font-families specifically for Microsoft Word rendering engines. In your Klaviyo campaign manager, make sure you configure your links to run via {% unsubscribe %}.
<!--[if mso]>
<style type="text/css">
body, table, td { font-family: Arial, sans-serif !important; }
</style>
<![endif]-->
<style>
@import url('https://fonts.googleapis.com/css2?family=Montserrat&display=swap');
</style>Live Code Sandbox Test
How to Deploy inside Klaviyo
Copy the fixed VML or table wrapper code block from the remediation box above.
Open your Klaviyo template editor. Drag an 'HTML' block directly into your layout timeline (do not use a standard text box). Clear the default skeleton content inside the Klaviyo markup editor and paste the RenderOps corrected inline code.