Fix Button Clickable Area Collapse in Mozilla Thunderbird — Brevo (Sendinblue) Guide 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 Button Clickable Area Collapse inside Mozilla Thunderbird templates when using Brevo (Sendinblue).
Technical Breakdown
Mozilla Thunderbird uses the Gecko which lacks support for standard rendering rules. This causes Button Clickable Area 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 maintain button structural size and clickable areas, apply paddings to the parent table cell (td tag) rather than the link element, and format the anchor tag style to display: block. 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" style="border-collapse:collapse;">
<tr>
<td bgcolor="#6366F1" style="padding: 10px 20px; border-radius: 4px;">
<a href="{{ unsubscribe }}" style="color: #ffffff; text-decoration: none; display: block; font-family: sans-serif; font-size: 14px; font-weight: bold;">Click Here</a>
</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.