Fix CSS Flexbox Collapse in Yahoo Mail — Campaign Monitor Guide for Editorial & Content Newsletters
Editorial newsletters rely on content layout readability and structural text spacing. If fonts default to Times New Roman or layout borders break, subscriber engagement metrics suffer. Below is the targeted integration guide to fix CSS Flexbox Collapse inside Yahoo Mail templates when using Campaign Monitor.
Technical Breakdown
Yahoo Mail uses the WebKit / Blink Web Wrapper which lacks support for standard rendering rules. This causes CSS Flexbox Collapse elements to break or collapse when rendering templates.
Campaign Monitor Behaviors
Campaign Monitor wraps custom blocks in dynamic edit tags, which can break the column flow inside Outlook. Ensuring correct class names is essential. Keep your editorial body clean. Strip redundant CSS class definitions using Vaporize to ensure the newsletter stays under Gmail's 102KB clipping ceiling.
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 Campaign Monitor 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
How to Deploy inside Campaign Monitor
Copy the fixed VML or table wrapper code block from the remediation box above.
In Campaign Monitor, click the 'Source' button on your selected editable text region, or edit the template code files directly. Ensure you append the 'class="cs-editable"' flag if you need inline editing later.