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Fix CSS Flexbox Collapse in iOS Mail (Apple) — Klaviyo Guide for Deliverability & Spam Audits

Spam filters analyze email HTML code quality alongside body copy. Unclosed tags, excessive styling block nesting, and broken link parameters are flagged as spam risks. Below is the targeted integration guide to fix CSS Flexbox Collapse inside iOS Mail (Apple) templates when using Klaviyo.

Technical Breakdown

iOS Mail (Apple) uses the WebKit Mobile which lacks support for standard rendering rules. This causes CSS Flexbox Collapse elements to break or collapse when rendering templates.

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. Run your finished layouts through the Spam Word Auditor to catch trigger phrases and verify structural delivery alignments before launching.

Remediation Code Block

To resolve this, modern layouts must be compiled down to Outlook-compliant nested HTML table models. Each flex container becomes a table row, and each flex child becomes a table data cell (td) with explicit pixel or percentage widths. In your Klaviyo campaign manager, make sure you configure your links to run via {% unsubscribe %}.

<table role="presentation" border="0" cellpadding="0" cellspacing="0" width="100%">
  <tr>
    <td width="50%" valign="top" style="padding: 20px;">Column 1</td>
    <td width="50%" valign="top" style="padding: 20px;">Column 2</td>
  </tr>
</table>

Live Code Sandbox Test

Interactive Klaviyo Custom Sandbox

Target Environment: iOS Mail (Apple)

How to Deploy inside Klaviyo

1

Copy the fixed VML or table wrapper code block from the remediation box above.

2

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.

Targeted Fixes by Use Case & Industry