Fix Button Clickable Area Collapse in Mozilla Thunderbird — Salesforce Marketing Cloud (SFMC) 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 Salesforce Marketing Cloud (SFMC).
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.
Salesforce Marketing Cloud (SFMC) Behaviors
SFMC's Content Builder wraps block exports in div frames that can break conditional comments. Additionally, AMPScript calls for personalizations can trigger parsing errors if they are inside MSO conditional comments. Ensure your AMPScript tags are evaluated *outside* the VML blocks. 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 Salesforce Marketing Cloud (SFMC) campaign manager, make sure you configure your links to run via %%unsubscribe_url%%.
<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_url%%" 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 Salesforce Marketing Cloud (SFMC)
Copy the fixed VML or table wrapper code block from the remediation box above.
Create an 'HTML content' layout block in Content Builder. Paste the table structure. Enclose any custom merge tags inside standard AMPscript wrapper lines.