# Error: Gmail could not authenticate

Source: https://catalystgroup.gg/docs/email-delivery/error-gmail-could-not-authenticate/
Updated: 2026-10-19 · By Duane Garner

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- **The app password was revoked**, or the Google password was changed (which removes all app passwords).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](https://catalystgroup.gg/docs/email-delivery/mailer-gmail/). 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

 
- Google limits how much mail a single account may send each day. A busy site will reach that limit and should use a dedicated mail service.
- If the error code is 534 rather than a plain "could not authenticate", see [534: application-specific password required](https://catalystgroup.gg/docs/email-delivery/error-534-app-password-required/).
- For any other SMTP host, see the general [535 Authentication failed](https://catalystgroup.gg/docs/email-delivery/error-535-authentication-failed/) article.

 

## Related

 
- [Google Workspace / Gmail](https://catalystgroup.gg/docs/email-delivery/mailer-gmail/)
- [Other SMTP](https://catalystgroup.gg/docs/email-delivery/mailer-other-smtp/)
- [Error: 534: application-specific password required](https://catalystgroup.gg/docs/email-delivery/error-534-app-password-required/)
- [Troubleshooting email delivery](https://catalystgroup.gg/docs/email-delivery/troubleshooting/)