Fix Gmail Line-Height Shifts in Mozilla Thunderbird — ActiveCampaign Guide for SaaS Product Operations
SaaS communications (onboarding guides, product updates, dashboard reports) require clean tech-first typography and functional UI component layout rendering. Below is the targeted integration guide to fix Gmail Line-Height Shifts inside Mozilla Thunderbird templates when using ActiveCampaign.
Technical Breakdown
Mozilla Thunderbird uses the Gecko which lacks support for standard rendering rules. This causes Gmail Line-Height Shifts elements to break or collapse when rendering templates.
ActiveCampaign Behaviors
ActiveCampaign's editor parses HTML template imports and automatically cleans inline attributes, which can break VML tags. Always use absolute styles and avoid relying on classes. Verify that your dashboard report layouts use nested tables. Flexbox layouts will fail in legacy Outlook clients used by enterprise software buyers.
Remediation Code Block
Define line-height as a unitless ratio (e.g. line-height: 1.4) or in explicit percentages (e.g. line-height: 140%). Avoid mixing em and px units, and apply the styles directly to the containing td or span tags containing typography. In your ActiveCampaign campaign manager, make sure you configure your links to run via %UNSUBSCRIBELINK%.
<p style="font-size: 16px; line-height: 22px; margin: 0; mso-line-height-rule: exactly;">Typography Paragraph</p>Live Code Sandbox Test
How to Deploy inside ActiveCampaign
Copy the fixed VML or table wrapper code block from the remediation box above.
Insert an 'HTML block' from the layout builder panels. Avoid standard text boxes, as the ActiveCampaign parser might strip conditional MSO comment strings on saving.