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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: Gmail could not authenticate

Updated

By Duane GarnerChief Executive Officer (CEO)
Summarize: Claude ChatGPT View Markdown
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Gmail's SMTP server refused the username and password saved in the Other SMTP mailer. Use an app password, or switch to the Gmail mailer.

This article is for sites that send through Gmail or Google Workspace using the Other SMTP mailer (host smtp.gmail.com), or through the Backup SMTP Transport on the Alerts tab, and see "Could not authenticate".

The error as you see it

SMTP Error: Could not authenticate. (with smtp.gmail.com as the host)

Shown by the Other SMTP mailer when it points at Gmail, in the failed-send banner ("Could not authenticate your SMTP account."), in Tools → Debug Events and in the Email Log.

What this error means

Your site connected to Gmail's SMTP server and offered the SMTP Username and SMTP Password, and Google said no. Google no longer accepts an account's normal password from apps like a WordPress plugin. It wants either an app password (a 16-character password made only for one app) or a proper OAuth connection, which the Google / Gmail mailer gives you.

Common causes

  • The normal Google password is saved in SMTP Password. Google blocks this sign-in method.
  • 2-Step Verification is off, so the account cannot create app passwords at all.
  • The app password was revoked, or the Google password was changed (which removes all app passwords).
  • The username is incomplete. It must be the full address, such as name@example.com.
  • A Google Workspace admin has turned off app passwords or SMTP access for the user.
  • Google flagged the sign-in as suspicious, often because your server is in a different country than you.

How to fix

  1. Consider the Gmail mailer instead

    The Google / Gmail mailer signs in with OAuth and avoids passwords entirely. In CRM-NG SMTP → Settings → General, choose it under Mailer and follow the Gmail setup guide. If you prefer to stay on SMTP, continue below.

  2. Turn on 2-Step Verification

    Signed in as the sending account, open https://myaccount.google.com/security and turn on 2-Step Verification.

  3. Create an app password

    Open https://myaccount.google.com/apppasswords, give it a name such as "WordPress site", and copy the 16-character password Google shows. You will not see it again.

  4. Workspace accounts

    If the app passwords page is missing, a Workspace admin must allow them: in https://admin.google.com/, the 2-Step Verification settings under Security → Authentication must be enforceable by users, and SMTP access must not be blocked for the user.

  5. Update the plugin settings

    In CRM-NG SMTP → Settings → General, with Other SMTP selected: set SMTP Host to smtp.gmail.com, Encryption to TLS with SMTP Port 587 (or SSL with 465), keep Authentication on, enter the full address in SMTP Username, use Remove Password, paste the app password (no spaces) into SMTP Password, and press Save Settings.

  6. 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." and the message appears in the account's Sent folder.

Notes

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