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.