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✉️ Email Delivery

Documentation, reference material and tutorials for CRM-NG SMTP Email: setup guides for every mail service, troubleshooting, and one article per error message.

Error: Could not connect to SMTP host

Updated

By Duane GarnerChief Executive Officer (CEO)
Summarize: Claude ChatGPT View Markdown
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CRM-NG SMTP could not open a connection to the mail server. Check host, port and encryption, then ask your host whether the port is blocked.

Shown by the Other SMTP and Zoho Mail mailers (and the backup SMTP transport)

The test result or the error log shows SMTP Error: Could not connect to SMTP host. or SMTP connect() failed, often with a lower-level reason underneath.

This article is for site owners sending through an SMTP server who get this error on a test email. It is the most common SMTP setup error.

What this error means

CRM-NG SMTP tried to reach the mail server at the host and port you entered and could not complete the connection. No login was attempted and no message was sent. This is a general message; the detail underneath, shown with View Error Log in the failed-send banner or in Tools → Debug Events, often says more, such as "connection refused" or "timed out".

Common causes

  • Your web host blocks outgoing connections on mail ports (25, 465, 587). Many shared hosts do this to stop spam. This is the most common cause.
  • SMTP Port and Encryption do not fit together. Port 465 needs SSL; port 587 needs TLS (or None with Auto TLS on); port 25 is usually plain.
  • A typo in SMTP Host.
  • The mail server does not accept connections from outside its own network, for example an internal Exchange server.
  • A firewall on your server or the mail provider's side blocks your server's IP.
  • The mail server is down for maintenance.

How to fix

  1. Check the provider's settings

    Look up the SMTP host, port and encryption in your mail provider's help pages or admin console.

  2. Correct CRM-NG SMTP

    Go to CRM-NG SMTP → Settings → General. Set SMTP Host, Encryption and SMTP Port to match. Leave Auto TLS on unless the provider says otherwise. Save.

  3. Try the other port

    If 587 with TLS fails, try 465 with SSL, or the reverse. Save each time and test.

  4. Ask your web host

    Ask whether the server can make outbound connections to your SMTP host on that port, and whether a firewall or security policy blocks it. Share the error log from CRM-NG SMTP → Tools → Debug Events.

  5. Send a test

    Go to CRM-NG SMTP → Tools → Email Test, fill in Send To and press Send Email.

Verify it worked

The test page shows "Test email sent successfully! Check your inbox to confirm delivery." If the error changes to an authentication error such as 535, the connection now works and only the login remains.

Notes

  • If your host will not open mail ports, switch to an API mailer such as SendLayer, Brevo, Mailgun or Amazon SES. API mailers send over normal HTTPS (port 443), which hosts almost never block.
  • For Microsoft 365 or Gmail, the 365 / Outlook and Google / Gmail mailers use APIs and avoid SMTP ports entirely.
  • Any error mentioning "connection" that CRM-NG SMTP cannot place more precisely links here.
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