double-opt-in-email

double-opt-in-email is a skill for Claude Code from mukul975/Privacy-Data-Protection-Skills. It costs 55 tokens per session (1,626 once invoked), scanned A, original, Apache-2.0.

A guide to double opt-in email subscriptions, where a person first requests emails and then confirms through a link sent to their inbox. It covers consent records and requirements relevant to laws such as the EU ePrivacy rules, CAN-SPAM, and Canada’s CASL.

In plain words
What is it for?
Use it to design newsletter or product-update sign-up flows, confirmation emails, consent tokens, subscription records, and unsubscribe or suppression handling across jurisdictions.
Why use it?
It helps verify that the address owner actually agreed to receive messages and prevents sending confirmation emails to addresses on a suppression list. It also addresses expiring links and keeping evidence of consent.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the consent-management-skills plugin — 14 skills shipped together

Good fit Use it to design newsletter or product-update sign-up flows, confirmation emails, consent tokens, subscription records, and unsubscribe or suppression handling across jurisdictions.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/mukul975/privacy-data-protection-skills/double-opt-in-email
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add mukul975/Privacy-Data-Protection-Skills --skill double-opt-in-email
Clone the repo
git clone --depth 1 https://github.com/mukul975/Privacy-Data-Protection-Skills

Made for: Claude Code.

Or install consent-management-skills, the plugin that ships this one along with the rest of its 14 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for double-opt-in-email

README.md
[![agentmods](https://agentmods.dev/badge/skills/mukul975/privacy-data-protection-skills/double-opt-in-email/github.svg)](https://agentmods.dev/skills/mukul975/privacy-data-protection-skills/double-opt-in-email)
Your own site
<a href="https://agentmods.dev/skills/mukul975/privacy-data-protection-skills/double-opt-in-email"><img src="https://agentmods.dev/badge/skills/mukul975/privacy-data-protection-skills/double-opt-in-email/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for double-opt-in-email

Your own site · 80×15
<a href="https://agentmods.dev/skills/mukul975/privacy-data-protection-skills/double-opt-in-email"><img src="https://agentmods.dev/badge/skills/mukul975/privacy-data-protection-skills/double-opt-in-email.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 55 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,626 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00055 $0.01626
Opus 5 $0.00028 $0.00813
Sonnet 5 $0.00011 $0.00325
Haiku 4.5 $0.00006 $0.00163

Measured 12d ago against content hash 5203c9ad6c21, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

double-opt-in-email scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 12d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/process.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/consent-management-skills/skills/double-opt-in-email/SKILL.md · 119 lines

How it starts

The opening of the file, as written. The whole thing — 119 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Implementing Double Opt-In Email

Overview

Double opt-in (DOI) is the gold standard for email marketing consent. It requires two steps: (1) the user submits their email address and indicates interest, and (2) the user clicks a confirmation link in a verification email. This creates a verifiable consent record that satisfies GDPR Article 7(1) (demonstrability), ePrivacy Directive Article 13 (prior consent for electronic marketing), and German Federal Court of Justice (BGH) rulings that have established DOI as the expected standard in Germany.

Double Opt-In Workflow

START: User enters email on CloudVault SaaS Inc. sign-up or newsletter form
  │
  ├─► Step 1: Initial Opt-In Request
  │     ├─ User enters email address
  │     ├─ User ticks unticked checkbox: "Send me product updates and news"
  │     ├─ Validate email format (RFC 5322)
  │     ├─ Check suppression list — if email is suppressed, do NOT send confirmation
  │     └─ Display: "Check your email to confirm your subscription."
  │
  ├─► Step 2: Generate Confirmation Token
  │     ├─ Create cryptographically random token (256-bit, URL-safe base64)
  │     ├─ Associate token with: email address, purpose, timestamp, IP, user agent
  │     ├─ Set expiration: 48 hours from generation
  │     └─ Store pending subscription record (status: "pending_confirmation")
  │
  ├─► Step 3: Send Confirmation Email
  │     ├─ From: [email protected]
  │     ├─ Subject: "Confirm your CloudVault newsletter subscription"
  │     ├─ Body:
  │     │   ├─ "You requested to receive product updates from CloudVault SaaS Inc."
  │     │   ├─ "Click below to confirm:"
  │     │   ├─ [Confirm Subscription] button → confirmation URL with token
  │     │   ├─ "If you didn't request this, you can ignore this email."
  │     │   ├─ "This link expires in 48 hours."
  │     │   └─ Controller details: CloudVault SaaS Inc., 42 Innovation Drive, Dublin
  │     ├─ Headers:
  │     │   ├─ List-Unsubscribe: <mailto:[email protected]>
  │     │   └─ List-Unsubscribe-Post: List-Unsubscribe=One-Click
  │     └─ Note: This confirmation email is NOT marketing — it is transactional
  │
  ├─► Step 4: User Clicks Confirmation Link
  │     ├─ Validate token: exists, not expired, not already used
  │     ├─ If valid:
  │     │   ├─ Update subscription status: "confirmed"
  │     │   ├─ Record consent with full audit trail:
  │     │   │   ├─ Initial request: timestamp, IP, user agent
  │     │   │   ├─ Confirmation: timestamp, IP, user agent
  │     │   │   └─ Consent text version hash
  │     │   ├─ Add email to active marketing list
  │     │   └─ Display: "Subscription confirmed! You'll receive updates from CloudVault."
  │     │
  │     ├─ If expired:
  │     │   ├─ Display: "This link has expired. Please subscribe again."
  │     │   └─ Delete pending record
  │     │
  │     └─ If already used:
  │           └─ Display: "You're already subscribed."
  │
  └─► Step 5: Ongoing Management
        ├─ Every marketing email includes one-click unsubscribe (RFC 8058)
        ├─ Unsubscribe adds to suppression list (permanent)
        ├─ Consent records retained for demonstration per Art. 7(1)
        └─ Re-consent requested after 24 months of inactivity

Read the full file on GitHub · 119 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 12d ago First seen · 119 lines · 55 tokens per session scan A 5203c9ad6c21

Subscribe to this mod's changes

double-opt-in-email is a skill published in the GitHub repository mukul975/Privacy-Data-Protection-Skills (272 stars, last pushed 5mo ago), licensed Apache-2.0. It adds 55 tokens to every session and 1,626 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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