public function get_headers( $headers = [] ): array {
		$from_email = $this->get_from_email();
		$from_name  = $this->get_from_name();

		// Enforce headers array.
		if ( ! is_array( $headers ) ) {
			$headers = explode( "\r\n", $headers );
		}

		// Add From name/email to headers if no headers set yet and we have a valid From email address.
		if ( empty( $headers ) && ! empty( $from_name ) && ! empty( $from_email ) && is_email( $from_email ) ) {
			$from_email = filter_var( $from_email, FILTER_SANITIZE_EMAIL );

			$headers[] = sprintf(
				'From: %1$s <%2$s>',
				stripcslashes( $from_name ),
				$from_email
			);

			$headers[] = sprintf(
				'Reply-To: %s',
				$from_email
			);
		}

		// Enforce text/html content type header.
		if ( ! in_array( 'Content-type: text/html', $headers, true ) || ! in_array( 'Content-type: text/html; charset=utf-8', $headers, true ) ) {
			$headers[] = 'Content-type: text/html; charset=utf-8';
		}

		/**
		 * Filter the headers.
		 *
		 * @since 5.5.9
		 *
		 * @param array          $headers The headers.
		 * @param string         $id      The email ID.
		 * @param Email_Abstract $this    The email object.
		 */
		$headers = apply_filters( 'tec_tickets_emails_headers', $headers, $this->id, $this );

		/**
		 * Filter the headers for the particular email.
		 *
		 * @since 5.5.10
		 *
		 * @param array          $headers The headers.
		 * @param string         $id      The email ID.
		 * @param Email_Abstract $this    The email object.
		 */
		$headers = apply_filters( "tec_tickets_emails_{$this->slug}_headers", $headers, $this->id, $this );

		return $headers;
	}