WordPress at a glance
function is not described

Automattic\WooCommerce\Admin\Notes\MerchantEmailNotifications

NotificationEmail::trigger() public WC 1.0

Trigger the sending of this email.

{} It's a method of the class: NotificationEmail{}

No Hooks.

Return

null. Nothing.

Usage

$NotificationEmail = new NotificationEmail();
$NotificationEmail->trigger( $user_email, $user_name );
$user_email(string) (required)
Email to send the note.
$user_name(string) (required)
User's name.

Code of NotificationEmail::trigger() WC 5.3.0

<?php
public function trigger( $user_email, $user_name ) {
	$this->recipient               = $user_email;
	$this->opened_tracking_url     = sprintf(
		'%1$s/wp-json/wc-analytics/admin/notes/tracker/%2$d',
		site_url(),
		$this->note->get_id()
	);
	$this->trigger_note_action_url = sprintf(
		'%1$s&external_redirect=1&note=%2$d&action=',
		wc_admin_url(),
		$this->note->get_id()
	);

	if ( $user_name ) {
		/* translators: %s = merchant name */
		$this->placeholders['{greetings}'] = sprintf( __( 'Hi %s,', 'woocommerce' ), $user_name );
	}

	$this->send(
		$this->get_recipient(),
		$this->get_subject(),
		$this->get_content(),
		$this->get_headers(),
		$this->get_attachments()
	);
}