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-capture.md

Email Capture Best Practices

Collecting email addresses responsibly with validation, verification, and proper consent.

Email Validation

Client-Side

HTML5:

<input type="email" required>

Best practices:

Validate on blur or with short debounce
Show clear error messages
Don't be too strict (allow unusual but valid formats)
Client-side validation ≠ deliverability

Server-Side (Recommended)

Always validate server-side—client-side can be bypassed.

Check:

Email format (RFC 5322)
Domain exists (DNS lookup)
Domain has MX records
Optionally: disposable email detection

Double opt-in

Confirms address belongs to user and is deliverable.

Process

User submits email
Send verification email with unique link/token
User clicks link
Mark as verified
Allow access/add to list

Timing: Send immediately, include expiration (24-48 hours), allow resend after 60 seconds, limit resend attempts (3/hour).

Single vs Double Opt-In

	Single Opt-In	Double Opt-In
Process	Add to list immediately	Require email confirmation first
Pros	Lower friction, faster growth	Verified addresses, better engagement, meets GDPR/CASL
Cons	Higher invalid rate, lower engagement	Some users don't confirm
Use for	Account creation, transactional	Marketing lists, newsletters

Recommendation: Double opt-in for all marketing emails.

Form Design

Email Input

Use type="email" for mobile keyboard
Include placeholder ("[email protected]")
Clear error messages ("Please enter a valid email address" not "Invalid")

Unchecked by default (required)
Specific language about what they're signing up for
Separate checkboxes for different email types
Link to privacy policy

☐ Subscribe to our weekly newsletter with product updates
☐ Send me promotional offers and deals

Don't: Pre-check boxes, use vague language, hide in terms.

Form Layout

Keep simple and focused
One primary action
Clear value proposition
Mobile-friendly
Accessible (labels, ARIA)

Error Handling

Invalid Email

Show clear error message
Suggest corrections for common typos (@gmial.com → @gmail.com)
Allow user to fix and resubmit

Already Registered

Accounts: "This email is already registered. [Sign in]"
Marketing: "You're already subscribed! [Manage preferences]"
Don't reveal if account exists (security)

Rate Limiting

Limit verification emails (3/hour per email)
Rate limit form submissions
Use CAPTCHA sparingly if needed
Monitor for abuse patterns

Verification Emails

Content:

Clear purpose ("Verify your email address")
Prominent verification button
Expiration time
Resend option
"I didn't request this" notice
Don't include OTP/2FA codes in subject line or preview text as it discourages opens

Design:

Mobile-friendly
Large, tappable button
Clear call-to-action

See Transactional Emails for detailed email design guidance.

Compliance - Legal requirements for consent (GDPR, CASL)
Marketing Emails - What happens after capture
Deliverability - How validation improves sender reputation

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.

Copywriting
Corey Haines· Community
Expert conversion copywriting for marketing pages that avoids AI-generated patterns and focuses on clarity, specificity, and customer-centric messaging.
Business and productivityClaude CodeClaude appsOpenAI Codex+14 more
MITGitHub stars of the source repository59k
Popups
Corey Haines· Community
Expert guidelines for designing and optimizing conversion-focused popups, modals, and banners that respect user experience.
Business and productivityClaude CodeClaude appsOpenAI Codex+14 more
MITGitHub stars of the source repository59k
Content Strategy
Corey Haines· Community
A strategic framework for planning, prioritizing, and managing content that drives traffic, builds authority, and generates leads.
Business and productivityClaude CodeClaude appsOpenAI Codex+14 more
MITGitHub stars of the source repository59k
Ad Creative
Corey Haines· Community
Generates and iterates on paid advertising creative, including headlines, ad copy, and visual concepts based on performance data and brand context.
Business and productivityClaude CodeClaude appsOpenAI Codex+14 more
MITGitHub stars of the source repository59k
Attribution
Corey Haines· Community
Analyze marketing performance by reconciling attribution models, tracking journeys, and identifying the true drivers of revenue.
Business and productivityClaude CodeClaude appsOpenAI Codex+14 more
MITGitHub stars of the source repository59k
Reverse Engineer Marketing
Corey Haines· Community
A growth analysis framework that reverse engineers competitor marketing strategies using public data to identify actionable growth plays.
Business and productivityClaude CodeClaude appsOpenAI Codex+14 more
MITLow riskHas scriptsGitHub stars of the source repository59k

Download ZIP

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