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://mp-staging.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/deliverability.md

Email Deliverability

Maximizing the chances that your emails are delivered successfully to the recipients.

Email Authentication

Required by Gmail/Yahoo/Microsoft - unauthenticated emails will be rejected or spam-filtered.

SPF (Sender Policy Framework)

Specifies which servers can send email for your domain.

v=spf1 include:amazonses.com ~all

Add TXT record to DNS
Use ~all (soft fail)

DKIM (DomainKeys Identified Mail)

Cryptographic signature proving email authenticity.

Your email service will provide you with a TXT record

DMARC

Policy for handling SPF/DKIM failures + reporting.

v=DMARC1; p=none; rua=mailto:[email protected]

Rollout: p=none (monitor) → p=quarantine; pct=25 → p=reject

Learn more: https://resend.com/blog/dmarc-policy-modes

Verify Your Setup

Check DNS records directly:

# SPF record
dig TXT example.com +short

# DKIM record (replace 'resend' with your selector)
dig TXT resend._domainkey.example.com +short

# DMARC record
dig TXT _dmarc.example.com +short

Expected output: Each command should return your configured record. No output = record missing.

Sender Reputation

IP Warming

New IP/domain? Gradually increase volume:

Week	Daily Volume
1	50-100
2	200-500
3	1,000-2,000
4	5,000-10,000

Start with engaged users. Send consistently. Don't rush.

Learn more: https://resend.com/docs/knowledge-base/warming-up

Maintaining Reputation

Do: Send to engaged users, keep bounce <4%, complaints <0.1%, remove inactive subscribers.

Don't: Send to purchased lists, ignore bounces/complaints, send inconsistent volumes

Bounce Handling

Type	Cause	Action
Hard bounce	Permanent failure to deliver	Remove immediately
Soft bounce	Transient failure to deliver	Retry: 1h → 4h → 24h, remove after 3-5 failures

Targets: <1% good, 1-3% acceptable, 3-4% concerning, >4% critical

Complaint Handling

Targets: <0.01% excellent, 0.01-0.05% good, >0.05% critical

Reduce complaints:

Only send to opted-in users
Make unsubscribe easy and immediate
Use clear sender names and "From" addresses

Feedback loops: Set up with Gmail (Postmaster Tools), Yahoo, Microsoft SNDS. Remove complainers immediately.

Infrastructure

Dedicated sending domain: Use different subdomains for different sending purposes (e.g., t.example.com for transactional emails and m.example.com for marketing emails).

DNS TTL: Low (300s) during setup, high (3600s+) after stable.

Troubleshooting

Emails going to spam? Check in order:

Authentication (SPF, DKIM, DMARC)
List-Unsubscribe header — required by Gmail/Yahoo since Feb 2024 (see Compliance)
Sender reputation (blacklists, complaint rates)
Content
Sending patterns (sudden volume spikes)

Diagnostic tools:

Google Postmaster Tools - Domain reputation and spam rates
mail-tester.com - Send a test email, get deliverability score
MXToolbox - Check blacklist status

List Management - Handle bounces and complaints to protect reputation
Sending Reliability - Retry logic and error handling

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