Email Best Practices

From the author

Use when building email features, emails going to spam, high bounce rates, setting up SPF/DKIM/DMARC authentication, implementing email capture, ensuring compliance (CAN-SPAM, GDPR, CASL), handling webhooks, retry logic, making emails accessible (alt text, headings, contrast, screen readers), or deciding transactional vs marketing.

— the description by Resend

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a structured framework for managing the entire lifecycle of email communications. It covers technical infrastructure like SPF/DKIM/DMARC authentication, legal compliance across major jurisdictions (GDPR, CAN-SPAM, CASL), and accessibility standards for screen readers and diverse email clients. It also offers guidance on transactional versus marketing email strategies, list management, and building reliable delivery pipelines with retry logic and webhooks.

What it does

Provides technical guidance for email authentication (SPF, DKIM, DMARC) to improve deliverability.
Outlines legal requirements for global email compliance including GDPR, CAN-SPAM, and CASL.
Defines accessibility standards for email content, including screen reader support and contrast.
Offers architectural patterns for transactional and marketing email workflows.
Details best practices for list management, bounce handling, and suppression lists.
Explains how to implement reliable sending with idempotency, retries, and webhook event tracking.

When to use it

When setting up a new email infrastructure for an application.
When troubleshooting high bounce rates or emails landing in spam folders.
When designing transactional email templates like password resets or order confirmations.
When implementing email capture forms that require legal consent tracking.
When auditing existing email templates for accessibility and compliance.

Advantages

Reduces the risk of legal penalties by providing clear compliance guidelines.
Improves email deliverability by standardizing authentication and list hygiene.
Ensures emails are accessible to all users, including those using assistive technology.
Provides a clear architectural path for building production-ready email systems.
Helps distinguish between transactional and marketing email strategies to optimize engagement.

Usage examples

“What are the legal requirements for sending marketing emails to users in the EU versus the US?”: The agent provides a comparison of GDPR and CAN-SPAM, highlighting the need for explicit opt-in consent for GDPR and the requirement for physical addresses and opt-out mechanisms for CAN-SPAM.
“How do I make my transactional email templates accessible for screen readers?”: The agent outlines specific HTML requirements, such as setting lang/dir attributes, using role='presentation' for layout tables, and ensuring proper heading hierarchy.
“My emails are going to spam. What should I check first?”: The agent directs the user to the deliverability reference to verify DNS authentication (SPF, DKIM, DMARC) and check for common configuration issues.

Install

Download the skill as a ZIP:
https://autogineer.com/agent-skills/resend/email-best-practices/download

Unzip it into the cross-client skills folder of your project:

mkdir -p .agents/skills && unzip email-best-practices.zip -d .agents/skills

Documentation by Resend

Guidance for building deliverable, compliant, user-friendly emails.

Architecture Overview

[User] → [Email Form] → [Validation] → [Double Opt-In]
                                              ↓
                                    [Consent Recorded]
                                              ↓
[Suppression Check] ←──────────────[Ready to Send]
        ↓
[Idempotent Send + Retry] ──────→ [Email API]
                                       ↓
                              [Webhook Events]
                                       ↓
              ┌────────┬────────┬─────────────┐
              ↓        ↓        ↓             ↓
         Delivered  Bounced  Complained  Opened/Clicked
                       ↓        ↓
              [Suppression List Updated]
                       ↓
              [List Hygiene Jobs]

Quick Reference

Need to...	See
Set up SPF/DKIM/DMARC, fix spam issues	Deliverability
Build password reset, OTP, confirmations	Transactional Emails
Plan which emails your app needs	Transactional Email Catalog
Build newsletter signup, validate emails	Email Capture
Send newsletters, promotions	Marketing Emails
Ensure CAN-SPAM/GDPR/CASL compliance	Compliance
Decide transactional vs marketing	Email Types
Handle retries, idempotency, errors	Sending Reliability
Process delivery events, set up webhooks	Webhooks & Events
Manage bounces, complaints, suppression	List Management
Make emails accessible (screen readers, alt text, contrast)	Accessibility

Start Here

New app? Start with the Catalog to plan which emails your app needs (password reset, verification, etc.), then set up Deliverability (DNS authentication) before sending your first email.

Spam issues? Check Deliverability first—authentication problems are the most common cause. Gmail/Yahoo reject unauthenticated emails.

Marketing emails? Follow this path: Email Capture (collect consent) → Compliance (legal requirements) → Marketing Emails (best practices).

Production-ready sending? Add reliability: Sending Reliability (retry + idempotency) → Webhooks & Events (track delivery) → List Management (handle bounces).

Accessibility? Most emails fail basic accessibility checks. See Accessibility for lang/dir, presentational tables, headings, alt text, <title>, and contrast.

Files

ATTRIBUTION.mdAdded by AutoGineer904 B
LICENSELicence file added by AutoGineer1.0 KiB
SKILL.md3.9 KiB
references/accessibility.md9.3 KiB
references/compliance.md4.1 KiB
references/deliverability.md3.3 KiB
references/email-capture.md3.4 KiB
references/email-types.md5.7 KiB
references/list-management.md4.5 KiB
references/marketing-emails.md3.2 KiB
references/sending-reliability.md4.5 KiB
references/transactional-email-catalog.md10.1 KiB
references/transactional-emails.md2.4 KiB
references/webhooks-events.md4.2 KiB

references/email-types.md

Email Types: Transactional vs Marketing

Understanding the difference between transactional and marketing emails is crucial for compliance, deliverability, and user experience. This guide explains the distinctions and provides a catalog of transactional emails your app should include.

When to Use This

Deciding whether an email should be transactional or marketing
Understanding legal distinctions between email types
Planning what transactional emails your app needs
Ensuring compliance with email regulations
Setting up separate sending infrastructure

Transactional vs Marketing: Key Differences

Transactional Emails

Definition: Emails that facilitate or confirm a transaction the user initiated or expects. They're directly related to an action the user took or are legal notices you're required to serve.

Characteristics:

User-initiated or expected
Time-sensitive and actionable
Required for the user to complete an action
Does not include promotional material or offers
Can be sent without explicit opt-in (with limitations)

Examples:

Password reset links
Order confirmations
Account verification
OTP/2FA codes
Shipping notifications

Analogy: Think of transactional emails for everything that would leave you with a paper receipt in the real world: invoices, parking ticket, booking confirmation, etc.

Marketing Emails

Definition: Emails sent for promotional, advertising, or informational purposes that are not directly related to a specific transaction or legal requirement.

Characteristics:

Promotional or informational content
Not time-sensitive to complete a transaction
Require explicit opt-in (consent)
Must include unsubscribe options
Subject to stricter compliance requirements

Examples:

Newsletters
Abandoned cart
Product announcements
Promotional offers
Company updates
Educational content

Legal Distinctions

CAN-SPAM Act (US)

Transactional emails:

Can be sent without opt-in
Must be related to a transaction
Cannot contain promotional content (with exceptions)
Must identify sender and provide contact information

Marketing emails:

Require opt-out mechanism (not opt-in in US)
Must include clear sender identification
Must include physical mailing address
Must honor opt-out requests within 10 business days

Transactional emails:

Can be sent based on legitimate interest or contract fulfillment
Must be necessary for service delivery
Cannot contain marketing content without consent

Marketing emails:

Require explicit opt-in consent
Must clearly state purpose of data collection
Must provide easy unsubscribe
Subject to data protection requirements

CASL (Canada)

Transactional emails:

Can be sent without consent if related to ongoing business relationship
Must be factual and not promotional

Marketing emails:

Require express or implied consent
Must include unsubscribe mechanism
Must identify sender clearly

When to Use Each Type

Use Transactional When:

User needs the email to complete an action
Email confirms a transaction or account change
Email provides security-related information
Email is expected based on user action
Content is time-sensitive and actionable
You're required to serve a notification for compliance

Use Marketing When:

Promoting products or services
Sending newsletters or updates
Sharing educational content
Announcing features or company news
Content is not required for a transaction

Hybrid Emails: The Gray Area

Some emails mix transactional and marketing content. This isn't best practice and should be avoided.

Best practice: Keep transactional and marketing separate.

Example of problematic hybrid:

Newsletter (marketing) with a small order status update (transactional)

Transactional Email Catalog

For a complete catalog of transactional emails and recommended combinations by app type, see Transactional Email Catalog.

Quick reference - Essential emails for most apps:

Email verification - Required for account creation
Password reset - Required for account recovery
Welcome email - Good user experience

The catalog includes detailed guidance for:

Authentication-focused apps
Newsletter / content platforms
E-commerce / marketplaces
SaaS / subscription services
Financial / fintech apps
Social / community platforms
Developer tools / API platforms
Healthcare / HIPAA-compliant apps

Sending Infrastructure

Separate subdomains

Best practice: Use separate sending subdomains for transactional and marketing emails.

Benefits:

Protect transactional deliverability
Different authentication domains
Independent reputation
Easier compliance management

Implementation:

Use different subdomains (e.g., t.example.com for transactional, m.example.com for marketing)

Email Service Considerations

Choose an email service that:

Provides reliable delivery for transactional emails
Offers separate sending domains
Has good API for programmatic sending
Provides webhooks for delivery events
Supports authentication setup (SPF, DKIM, DMARC)

Services like Resend are designed for transactional emails and provide the infrastructure and tools needed for reliable delivery. They also offer powerful marketing features.

Transactional Emails - Best practices for sending transactional emails
Marketing Emails - Best practices for marketing emails
Compliance - Legal requirements for each email type
Deliverability - Ensuring transactional emails are delivered

Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Security

No issues found by our static scan· No issues found

A static scan is not a guarantee. Skills are third-party content: review a skill before you let an agent use it.

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Download ZIP

The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download email-best-practices.zip

From the author

AutoGineer summary

What it does

When to use it

Advantages

Usage examples

Install

Documentation by Resend