Resend
Connect Resend to send transactional and batch email, and manage domains, broadcasts, contacts, and templates.
You end up pasting a single Resend API key that starts with re_ and is shown once, at creation time.
- Setup time
- 2 min
- Auth
- API credentials
- API base URL
- https://api.resend.com
- Rate limits
- Default maximum of 10 requests per second per team. Exceeding it returns 429.
Before you begin
- Resend account. The free tier is enough.
- Membership of the Resend team with permission to create API keys
- A verified sending domain if you want to send from your own domain instead of onboarding@resend.dev
Get your credentials
Open the API Keys page
Sign in at resend.com and click API Keys in the left sidebar, or go straight to resend.com/api-keys.
API Keys
Keys used to authenticate requests to the Resend API.
| Name | Token | Permission | Last used | Created |
|---|---|---|---|---|
| ProductionAll domains | re_9ax****4f2c | Full access | 2 hours ago | Mar 4, 2026 |
| Marketing siteacme.com | re_2kd****81be | Sending access | 6 days ago | Feb 11, 2026 |
| Old staging keyAll domains | re_4mp****d073 | Full access | Never used | Nov 2, 2025 |
Existing keys only ever show a masked prefix. A key value cannot be read again after creation.
Click Create API Key
Press Create API Key at the top right of the page. A dialog opens with a name, a permission and a domain.
Name the key and pick a permission
Type PopMCP in Name, choose Full access for every Resend tool or Sending access for a send-only connection, then click Add. Sending access also lets you lock the key to one domain.
API Keys
Keys used to authenticate requests to the Resend API.
Name is limited to 50 characters.
Copy the key straight away
Resend reveals the full re_ key once. Click Copy before you close the dialog.
API Keys
Keys used to authenticate requests to the Resend API.
Paste the key into PopMCP
Paste the value into the PopMCP API key field and save.
Connect in PopMCP
Open your workspace, choose Resend in the marketplace, and fill in the connect dialog:
| Field | What to enter |
|---|---|
| API keysecret | Resend → API Keys → Create API Key. Choose Full access for all tools, or Sending access for send-only. Copy the key (shown once). Stored encrypted.Encrypted with AES-256-GCM on save and never shown again. |
PopMCP verifies the credential against Resend immediately. On success the connection flips to Verified and its MCP tools are provisioned.
Verify it worked
PopMCP shows the Resend connector as Connected. Listing your domains returns the domains in that Resend team. A sending-only key returns a permission error on that tool instead, which still confirms the key is valid.
Troubleshooting
401 Unauthorized, "API key is invalid"
Why: The key was truncated on paste, or it was deleted from the Resend dashboard.
Fix: Create a fresh key on resend.com/api-keys and paste the whole `re_` string with no surrounding spaces.
403 restricted_api_key
Why: A Sending access key was used for a tool that reads or writes domains, contacts or broadcasts.
Fix: Create a new key with Full access and reconnect.
403 validation_error, domain is not verified
Why: You are sending from a domain that has not completed DNS verification.
Fix: Verify the domain under **Domains** in the Resend dashboard, or send from onboarding@resend.dev while testing.
429 rate_limit_exceeded
Why: More than the default 10 requests per second per team.
Fix: Batch your sends or slow the calls down. Ask Resend support to raise the limit for high-volume accounts.
You lost the key value
Why: Resend never displays a key again after the creation dialog closes.
Fix: Remove the old key from the row menu under **More options**, then create a replacement.