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How to Fix CSS Flexbox Collapse in Outlook 2016
for HubSpot Campaigns

A programmatic integration guide for resolving email rendering crashes inside Outlook 2016 using HubSpot's layout editor environment.

Root Bug Analysis

Outlook 2016 desktop uses Word's layout engine, stripping flex directions and stacking columns vertically.

Active rendering engine: Microsoft Word (MSO)

HubSpot Specific Guide

HubSpot's drag-and-drop parser wraps custom layout grids in nested wrappers, causing table cells to misalign inside Outlook.

Integration Step:

In HubSpot's Design Manager, edit the modules section. Create a 'Rich Text' or 'HTML' module block. Double-click the block, choose 'Tools' or 'Advanced', click 'Source Code', and drop the code snippet inside.

ESP Unsubscribe Alignment

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

HubSpot Unsubscribe Tag:{{ unsubscribe_link }}

Documented Client Behavior

Expected layout behavior based on target rendering engine specifications:

Documented behavior: Flex boxes display as single-column stacks in Outlook 2016 desktop viewports. Table constraints must be embedded inline.

Interactive HubSpot Custom Sandbox

Target Environment: Outlook 2016

Paste Your Broken Code

<div style="display: flex;">
  <div>Col 1</div>
  <div>Col 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 2016.

Launch Retrofit Compiler

How to Fix CSS Flexbox Collapse in Outlook 2016 for HubSpot Campaigns