Returning a non-null value will short-circuit wp_mail(), returning that value instead. A boolean return value should be used to indicate whether the email was successfully sent.
Parameters
$returnnull|bool
Short-circuit return value.
$attsarray
{ Array of the wp_mail() arguments. @type string|string[] $to Array or comma-separated list of email addresses to send message. @type string $subject Email subject. @type string $message Message contents. @type string|string[] $headers Additional headers. @type string|string[] $attachments Paths to files to attach. @type string|string[] $embeds Paths to files to embed.}
$tostring|string[]
Array or comma-separated list of email addresses to send message.