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Fix CSS Flexbox Collapse in iOS Mail (Apple) — Brevo (Sendinblue) Guide

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

Root Bug Analysis

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.

Active rendering engine: WebKit Mobile

Brevo (Sendinblue) Specific Guide

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

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 iOS Mail (Apple) when templates are sent from Brevo (Sendinblue).

Interactive Brevo (Sendinblue) Custom Sandbox

Target Environment: iOS Mail (Apple)

Auto-compile fixes inside RenderOps Workspace

Load layout code directly into our Retrofit Compiler to compile responsive table frameworks that display cleanly in iOS Mail (Apple).

Launch Retrofit Compiler

Fix CSS Flexbox Collapse on Other clients for Brevo (Sendinblue)