You cannot use Brevo SMTP now because wp_mail has been declared by another proc

Hi,

We have a WordPress site that uses WooCommerce and we need to send emails via Brevo using this plugin.

However, after activating and connecting with our Brevo account, this is the error message we get on the plugin settings page:

You cannot use Brevo SMTP now because wp_mail has been declared by another process or plugin.

We don’t have any other SMTP plugins installed.

We tried to check which process is interfering with the Brevo plugin using this code:

$ref = new ReflectionFunction('wp_mail');
echo $ref->getFileName() . ‘ lines ’ . $ref->getStartLine() . ' - ' . $ref->getEndLine();

// we put this code directly in the Brevo plugin right before the existing check that triggers the error message above

The output shows that wp_mail is already declared by WordPress itself:

<website_directory>/wp-includes/pluggable.php lines 189 - 665

Is there an issue with the plugin, or are there known compatibility issues? But I don’t see how this is caused by another plugin since it’s defined by WordPress and not a different plugin.

Any help appreciated!

Best,
Linus