Phixo – explains why an email in Gmail/Outlook is phishing

Mailpeek – Vue.js email preview component (Gmail/Outlook rendering)

Renders email HTML inside an iframe with client-specific CSS filtering (Gmail vs Outlook vs raw), responsive device presets, and a handy 102KB Gmail clipping warning — small but pragmatic features that speed up local iteration. Zero runtime dependencies, TypeScript types and SSR compatibility make it easy to drop into modern Vue/Nuxt stacks; don’t expect it to fully replace real-client testing services like Litmus, but it’s an excellent dev-time preview tool.