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Outlook Email Broken Layout Fix: Resolve CSS Flexbox Collapse

A programmatic integration guide for resolving email rendering crashes inside Outlook 2021 using Brevo (Sendinblue)'s layout editor environment.

Root Bug Analysis

Outlook 2021 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.

Active rendering engine: Microsoft Word (MSO)

Brevo (Sendinblue) Specific Guide

Brevo (Sendinblue)'s delivery wrapper can clean and restructure elements during import, creating dynamic spacing differences inside Outlook 2021.

Integration Step:

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.

ESP Unsubscribe Alignment

When compiling custom HTML templates for Brevo (Sendinblue), you must ensure your layout retains deliverability compliance loops. Brevo (Sendinblue) requires you to insert their specific unsubscribe merge tag, otherwise your campaign delivery will be flagged by automated spam audits.

Brevo (Sendinblue) Unsubscribe Tag:{{ unsubscribe }}

Documented Client Behavior

Expected layout behavior based on target rendering engine specifications:

Documented behavior: CSS Flexbox Collapse causes elements to stack vertically or clip in Outlook 2021 when templates are sent from Brevo (Sendinblue).

Interactive Brevo (Sendinblue) Custom Sandbox

Target Environment: Outlook 2021

Paste Your Broken Code

<div style="display: flex; justify-content: space-between;">
  <div style="width: 280px; padding: 20px;">Column 1</div>
  <div style="width: 280px; padding: 20px;">Column 2</div>
</div>

RenderOps Compiled Output

<!-- Paste code on the left and click compile to output clean fallback tags -->

Auto-compile fixes inside RenderOps Workspace

Load layout code directly into our Retrofit Compiler to compile responsive table frameworks that display cleanly in Outlook 2021.

Launch Retrofit Compiler