Overview
The ‘Error 535’ issue often occurs on sites attempting to send emails through an SMTP server. It indicates the credentials you used to set up your SMTP plugin are invalid.
Causes
This error typically occurs when:
- The email account password has been changed recently
- The username (often the email address) is entered incorrectly
- The password or API key is entered incorrectly
- The authentication method used is not supported by the server
Solution
To resolve this issue, we suggest:
- Double-checking the username and password for accuracy
- Verifying that the account has SMTP access enabled
- Checking if any recent security changes or two-factor authentication might be preventing your account from connecting to the SMTP plugin
If you’re using an SMTP plugin such as WP Mail SMTP, you may need to run through the setup process for your chosen mailer.
That’s it! Now you know how to troubleshoot and fix the ‘Error 535: Authentication credentials are invalid’ error.
Want to explore other mailers WP Mail SMTP provides to improve email deliverability? Be sure to check out our complete guide to WP Mail SMTP mailers.