Responsive email newsletter template design

We are launching a regular email newsletter and need a designer to build us a responsive HTML email template. The key requirement is a modular structure: I want a set of ready-made blocks — a header with our logo, a large hero banner, product cards in two columns, a text block with a heading, a call-to-action button, dividers, and a footer with contact details and social links — that our marketing team can assemble into campaigns without touching code. The template must render correctly on mobile: columns should collapse into a single column, font sizes must stay readable, and buttons should be large and easy to tap with a finger. Please pay special attention to dark mode support, so the logo and icons do not disappear against a dark background and text colors invert gracefully wherever the client supports it. I need bulletproof buttons that look identical in Outlook and Gmail. Compatibility testing across the major email clients is mandatory: Gmail (web and app), several versions of Outlook, Apple Mail and common regional providers. Deliverables should include the source files, ready-to-use HTML with inlined styles, and a short guide explaining how to assemble emails from the blocks. A portfolio with real email examples is required.