Resend Email Skill

Send emails via the Resend transactional email API.

IMPORTANT: Confirm Before Sending

Always confirm with the user before sending an email. Show them the recipient(s), subject, and body content and get explicit approval. Email is not reversible.

When to Use This Skill

• Sending a transactional or notification email
• Sending HTML email (inline or from a file)
• Sending email with attachments
• Piping content from another command into an email body

Prerequisites

1. API Key: Get a Resend API key at https://resend.com/api-keys (format: re_xxxxxxxxx)
2. Add to secrets: Add export RESEND_API_KEY=re_xxxxxxxxx to ~/.config/env/secrets.env
3. Verify domain (optional): By default, send from onboarding@resend.dev (test only). For production, verify a domain at https://resend.com/domains
4. Install requests: uv pip install --system requests

Credentials checked in order: RESEND_API_KEY env var > ~/.config/env/secrets.env > ~/.claude.json

Quick Start

# Simple text email
python3 ~/.claude/skills/resend/scripts/send.py \
  --to "recipient@example.com" \
  --subject "Hello from Claude" \
  --body "This is a test email."

# HTML email from a file
python3 ~/.claude/skills/resend/scripts/send.py \
  --to "recipient@example.com" \
  --subject "Weekly Report" \
  --html report.html

# Pipe content as body
echo "Pipeline output here" | python3 ~/.claude/skills/resend/scripts/send.py \
  --to "recipient@example.com" \
  --subject "Build Results"

# Multiple recipients with CC
python3 ~/.claude/skills/resend/scripts/send.py \
  --to "alice@example.com" "bob@example.com" \
  --cc "manager@example.com" \
  --subject "Meeting Notes" \
  --body "Attached are the notes from today."

# With attachments
python3 ~/.claude/skills/resend/scripts/send.py \
  --to "recipient@example.com" \
  --subject "Invoice" \
  --body "Please find the invoice attached." \
  --attachments invoice.pdf

# Custom from address (requires verified domain)
python3 ~/.claude/skills/resend/scripts/send.py \
  --from "tom@minoanmystery.org" \
  --to "recipient@example.com" \
  --subject "Test" \
  --body "Sent from a verified domain."

# Inline HTML string
python3 ~/.claude/skills/resend/scripts/send.py \
  --to "recipient@example.com" \
  --subject "Styled Email" \
  --html "<h1>Hello</h1><p>This is <strong>bold</strong>.</p>"

# Dry run (print payload without sending)
python3 ~/.claude/skills/resend/scripts/send.py \
  --to "recipient@example.com" \
  --subject "Test" \
  --body "Hello" \
  --dry-run

Parameters

python3 ~/.claude/skills/resend/scripts/send.py [OPTIONS]

Flag	Description	Required
--to EMAIL [EMAIL...]	Recipient email address(es)	Yes
--subject TEXT	Email subject line	Yes
--body TEXT	Plain text body (or pipe via stdin)	One of --body, --html, or stdin
--html FILE_OR_STRING	HTML body: path to .html file, or inline HTML string	One of --body, --html, or stdin
--from EMAIL	Sender address (default: Tom di Mino <tom@send.minoanmystery.org>)	No
--cc EMAIL [EMAIL...]	CC recipients	No
--bcc EMAIL [EMAIL...]	BCC recipients	No
--reply-to EMAIL	Reply-to address	No
--attachments FILE [FILE...]	File paths to attach	No
--dry-run	Print the payload without sending	No

Body resolution: --body and --html can be combined for multipart email (text + HTML). If neither is provided, stdin is used as plain text. --body "" sends an empty text part.

Sender Aliases

Use --from ALIAS as a shorthand for named senders:

Alias	Expands to
tom	Tom di Mino <tom@send.minoanmystery.org>
kothar	Kothar wa Khasis <kothar@send.minoanmystery.org>
claudius	Claudius, Artifex Maximus <claudius@send.minoanmystery.org>
minoan	Minoan Mystery <contact@send.minoanmystery.org>

# Send as Kothar
--from kothar

# Send as Claudius
--from claudius

If --from doesn't match an alias, it's used as-is (full email or Name <email> format).

Test Addresses

Resend provides test addresses that don't affect domain reputation:

• delivered@resend.dev — simulates successful delivery
• bounced@resend.dev — simulates a bounce

Rate Limits

Resend enforces 2 requests per second. The script does not batch or retry — if sending multiple emails, add a 1-second delay between invocations.

Troubleshooting

Problem	Fix
RESEND_API_KEY not found	Add export RESEND_API_KEY=re_xxx to ~/.config/env/secrets.env
missing_required_field	Ensure --to and --subject are provided, plus body content
validation_error on from	Default onboarding@resend.dev only works for test sends. Verify a domain at resend.com/domains
rate_limit_exceeded	Wait 1 second between sends (2 req/s limit)
Attachment not found	Use absolute paths or paths relative to CWD