SMTP Error "Connection closed unexpectedly" with Gmail on n8n Cloud (Works perfectly in GMass)

Questions
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1

Hi everyone,

I am running into a persistent issue trying to set up the Send Email node using Gmail SMTP on n8n Cloud.

I have verified my credentials multiple times, and they work perfectly in external SMTP testing tools (GMass), but I keep getting a Connection closed unexpectedly error inside n8n.

My Goal

I want to send emails via the SMTP node using a custom domain alias ([email protected]) that I have set up in my Gmail account. I prefer the SMTP node over the Gmail node to ensure I can strictly control the “From” address for my business domain.

The Setup

  • Platform: n8n Cloud

  • SMTP Host: smtp.gmail.com

  • Username: [email protected] (My main Gmail account)

  • Password: A fresh 16-digit Google App Password (2FA is on)

Evidence that Credentials work

I tested these exact credentials in GMass (SMTP Test Tool), and the connection was successful. I was able to send a test email from [email protected] to another address without issues.

  • GMass Config: Port 587, TLS, Auth Plain.

  • Result: 250 2.0.0 OK (Email sent successfully).

What I have tried in n8n (and failed)

I have tried every combination of ports and SSL/TLS toggles in the n8n credential settings, but nothing works:

Attempt 1 (Standard TLS):

  • Port: 587

  • Secure: OFF (Toggled OFF because 587 uses STARTTLS)

  • Ignore SSL Issues: ON

  • Result: Connection closed unexpectedly

Attempt 2 (SSL):

  • Port: 465

  • Secure: ON (Toggled ON for SSL)

  • Ignore SSL Issues: ON

  • Result: Connection closed unexpectedly / Timeout

Steps taken so far

  1. Deleted and recreated the App Password in Google.

  2. Verified that [email protected] is set up correctly as a “Send mail as” alias in Gmail settings.

  3. Confirmed that I am using the main Gmail address ([email protected]) in the User field of the credentials, not the alias.

  4. Tried toggling “Ignore SSL Issues” both on and off.

Since I am on n8n Cloud, I assume ports 587/465 shouldn’t be blocked (unlike self-hosted AWS/DigitalOcean).

Has anyone else faced this “Connection closed unexpectedly” error specifically on n8n Cloud with Gmail recently? Is there a specific hidden setting I am missing?

Any help would be appreciated!

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1 Like
2

Looks like you’ve got the right credentials and settings. You could try enabling “Use STARTTLS” in the SMTP node’s configuration. Let me know if this works!

3

Hi, same issue here, additionally I’ve tested removing the whitespaces into the app password as I don’t know if they are relevant or not. The error message is quite vague.

Using the dedicated Gmail node is irrelevant as it requires a convoluted oauth2 setup and SMTP should work out-of-the-box.

This is perhaps some security measure from Google?

Related: Connection closed unexpectedly error during sending email via Send Email node with gmail credentials