Does Postmark include a built-in CSS inliner?

Postmark provides basic functionality but lacks granular control. Postmark requires you to inline CSS yourself. Their MailMason templates use MJML which compiles to inlined HTML at build time.

Is there a free way to CSS inlining for Postmark campaigns?

Yes. The MiN8T CSS Inliner below runs entirely in your browser — no signup, no upload, and the output works with any Postmark workflow.

What image size limit does Postmark enforce?

Postmark accepts uploads up to 5000 KB per image and recommends a max width of 600px for email body width. Supported formats: JPG, PNG, GIF, WebP.

Works with Postmark

CSS Inliner for Postmark: Free Browser-Based Tool

→ Open the free CSS Inliner

Browser-only, no signup, no upload. Output works with any Postmark campaign.

Built by the MiN8T Engineering Team · Updated 28 May 2026

Postmark's built-in tools cover the basics, but the CSS inliner workflow often benefits from a dedicated, browser-only preprocessor before uploading. Outlook desktop (Word rendering engine) ignores