subject-line-lab

Generate and pre-score email subject line variants on spam triggers and truncation.

2.5k|345|Updated Dec 18, 2025
One-click install
npx skills add https://github.com/aaron-he-zhu/aaron-marketing-skills --skill subject-line-lab
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: subject-line-lab
Source: https://github.com/aaron-he-zhu/aaron-marketing-skills/tree/main/email/engage/subject-line-lab
Command: npx skills add https://github.com/aaron-he-zhu/aaron-marketing-skills --skill subject-line-lab

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes scripts (resource) and references (resource) components.

What problem does it solve?

This Skill automates the process of generating and pre-scoring email subject lines, saving time and reducing the risk of ineffective communication.

Core Features & Use Cases

  • Subject Line Generation: Draft 3-8 angle-labeled variants and pre-score them.
  • Pre-Scored Results: Provides spam-trigger flags, length/truncation across desktop + mobile, emoji-count, and the inbox preview render.
  • Use Case: Before sending an email campaign, use this Skill to generate and evaluate multiple subject line options, ensuring the best engagement rates.

Quick Start

Pre-score these 6 subject lines for truncation + spam triggers, from-name [Sender], promo mode: [paste]

Frequently Asked Questions about subject-line-lab

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I pre-score email subject lines for spam triggers and truncation?

You can generate 3-8 angle-labeled subject line variants by providing a campaign angle, from-name, and mode (B2C promo/lifecycle, B2B cold-outbound, or newsletter). The tool drafts multiple options tailored to your specific email marketing campaign context.

Can I evaluate existing email subject candidates for spam detection?

Yes, you can evaluate existing email subject candidates by pasting them into the tool. It analyzes your provided subject lines for spam-trigger patterns, length/truncation issues, and emoji count, returning a pre-scored report for your email campaign.

Does email subject line generation work for B2B cold-outbound campaigns?

Yes, email subject line generation works for B2B cold-outbound campaigns, as well as B2C promo/lifecycle and newsletter modes. You simply select the appropriate mode and provide the required from-name and angle to generate tailored variants.

What do I need to generate and pre-score subject lines for an email campaign?

To generate and pre-score subject lines, you need to input your subject candidates or angle, the from-name, and the specific campaign mode (promo, lifecycle, cold-outbound, or newsletter). The tool then outputs variants with spam-trigger flags and render previews.

Why does my email subject line get truncated on mobile devices?

Email subject lines get truncated on mobile devices due to character length limits. The pre-score feature checks length and truncation across both desktop and mobile views, helping you identify and adjust subject lines that exceed display limits before sending.