The ‘Could not authenticate’ SMTP error often occurs with the Other SMTP mailer.
You may experience this error if the app password you generated doesn’t match the one you entered when configuring your SMTP plugin.
Also, the Other SMTP mailer is less secure and doesn’t use a dedicated API to authenticate emails. This can result in your web hosting provider blocking emails from the SMTP server you configured.
Resolving the Error – Solution
If the issue is caused by misconfiguration of your SMTP plugin, we recommend double-checking that you’ve copied the correct SMTP server details from your email service provider. You may need to re-run the setup process to confirm everything is configured properly.
Note: If you’re using Easy WP SMTP and need to run through the configuration process, be sure to check out this guide to setting up the Other SMTP mailer with Easy WP SMTP.
If the issue is server-related, reach out to your web hosting provider with the specific error details for further guidance.
However, we recommend switching to a transactional email service provider such as SendLayer to avoid such issues.
Doing so will ensure your emails are sent via a secure API-based SMTP server.
Note: For a detailed guideline, be sure to check out Easy WP SMTP’s tutorial on setting up the SendLayer mailer.