Hi @123maxine ,
Thanks for reaching out.
This error (Mailer: Brevo unauthorized: authentication not found in header) typically means that Brevo (formerly Sendinblue) is rejecting the email request due to missing or incorrect authentication credentials—often the API key. Basically, WP Mail SMTP is trying to send the email through Brevo, but Brevo doesn’t recognize or accept the request because the necessary authentication details are either missing or invalid.
To fix this issue, I’d recommend the following steps:
- Double-check your Brevo API key in WP Mail SMTP settings:
Go to WP Mail SMTP → Settings → Mailer → Brevo and make sure the API key entered there is correct and still active.
- Re-authenticate the mailer if needed:
You may want to generate a new API key from your Brevo account and update it in your site’s settings. Here’s a step-by-step guide that walks you through setting up Brevo correctly with WP Mail SMTP: How to Set Up Brevo with WP Mail SMTP
- Send a test email again from WP Mail SMTP after updating the API key to confirm everything is working properly.
I hope this helps. Thanks 🙂
