# SMTP2GO

Source: https://catalystgroup.gg/docs/email-delivery/mailer-smtp2go/
Updated: 2026-10-19 · By Duane Garner

Connect CRM-NG SMTP to SMTP2GO with an API key that can send email and a verified sender domain.

This guide shows you how to send your WordPress email through SMTP2GO, an email delivery service with servers around the world. It suits small and medium sites that want straightforward setup and clear delivery reports. SMTP2GO has a free plan with a monthly limit; check its site for the current allowance.

 

The **SMTP2GO** mailer sends through SMTP2GO's API with an API key. You also verify the domain you send from, so receivers can trust your mail.

 

## Before you start

 
- An SMTP2GO account (sign up at `https://www.smtp2go.com/`). New accounts may need a quick review before sending freely.
- A domain you control, with access to its DNS records.
- Administrator access to your WordPress site.

 

## Step 1: Verify your sender domain

 
1. Sign in to SMTP2GO
  Go to `https://app.smtp2go.com/` and sign in.
2. Open Verified Senders
  Open **Sending → Verified Senders**.
3. Add a sender domain
  Choose to add a sender domain and enter the domain you send from, for example `yourdomain.com`.
4. Publish the records
  SMTP2GO shows a few CNAME records (for DKIM, the return path and link tracking). Add them at your DNS provider exactly as shown.
5. Verify
  Return to SMTP2GO and press the verify button until the domain shows as verified.

 

You can verify a single sender email address instead, but a verified domain gives better delivery. See [Adding DNS records](https://catalystgroup.gg/docs/email-delivery/dns-records/).

 

## Step 2: Create an API key

 
1. Open API Keys
  In SMTP2GO, open **Sending → API Keys**.
2. Add a key
  Choose **Add API Key**. Give it a description such as your site name.
3. Check its permissions
  Open the key's permissions (look for a list of API endpoints or permission groups). Make sure the email sending endpoint is allowed. A key restricted to other endpoints will be refused when the site tries to send.
4. Copy the key
  Copy the key, which starts with `api-`.

 

## Step 3: Connect in CRM-NG SMTP

 
1. Choose the mailer
  In WordPress, open **CRM-NG SMTP → Settings → General** and set **Mailer** to **SMTP2GO**.
2. Paste the key
  Paste the key into **API Key**.
3. Set the sender
  Set **From Email** to an address on your verified domain and set **From Name**. Tick **Force From Email** if other plugins change the sender.
4. Save
  Press **Save Settings**.

 

To remove the key later, use **Remove API Key** next to the field.

 

## Send a test email

 

Open **CRM-NG SMTP → Tools → Email Test**, enter your address in **Send To**, and press **Send Email**. In SMTP2GO, the activity or reports page shows the message and its delivery status. See [Sending a test email](https://catalystgroup.gg/docs/email-delivery/send-a-test-email/).

 

## Troubleshooting

 
- The key is not allowed to use the send endpoint: [ENDPOINT_PERMISSION_DENIED](https://catalystgroup.gg/docs/email-delivery/error-smtp2go-endpoint-permission-denied/)
- The key is wrong or deleted: [Invalid API key](https://catalystgroup.gg/docs/email-delivery/error-invalid-api-key/) and [401 Unauthorized or Forbidden](https://catalystgroup.gg/docs/email-delivery/error-401-unauthorized-or-forbidden/)
- The From address is not a verified sender: [553 Sender address rejected](https://catalystgroup.gg/docs/email-delivery/error-553-sender-address-rejected/)
- You have reached your monthly limit: [Email sending limit reached](https://catalystgroup.gg/docs/email-delivery/error-email-sending-limit/)
- The recipient bounced before and is blocked: [Email address in suppression list](https://catalystgroup.gg/docs/email-delivery/error-email-in-suppression-list/)
- Mail arrives in spam: [Emails landing in spam](https://catalystgroup.gg/docs/email-delivery/emails-landing-in-spam/)

 

## Related

 
- [Choosing a mail service](https://catalystgroup.gg/docs/email-delivery/choose-a-mailer/)
- [Adding DNS records: SPF, DKIM and DMARC](https://catalystgroup.gg/docs/email-delivery/dns-records/)
- [Verifying your DNS records](https://catalystgroup.gg/docs/email-delivery/verify-dns-records/)
- [Sender name, address and the Force settings](https://catalystgroup.gg/docs/email-delivery/sender-name-and-address/)
- [Debug events](https://catalystgroup.gg/docs/email-delivery/debug-events/)