Outlook Email Broken Layout Fix: Resolve CSS Flexbox Collapse 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 CSS Flexbox Collapse inside Outlook 2016 templates when using Brevo (Sendinblue).
Technical Breakdown
Outlook 2016 uses the Microsoft Word (MSO) which lacks support for standard rendering rules. This causes CSS Flexbox Collapse elements to break or collapse when rendering templates.
Brevo (Sendinblue) Behaviors
Brevo's rendering system injects inline spacing helpers to support their responsive editor, which can cause column overlaps in Outlook. Using explicit table alignments is required. 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 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 Brevo (Sendinblue) 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 Brevo (Sendinblue)
Copy the fixed VML or table wrapper code block from the remediation box above.
Open Brevo's template canvas, select the element you wish to configure, click 'Edit HTML' or insert a standalone 'HTML' content block, and paste the code.