Can't not send mail (Openlitespeed +Wordpress + Woocommerce)

Hi guys,
I m using VPS-ubuntu (GCP) and integrate Openlitespeed + woocommerce + wordpress. But it seems the site can't send the bill to customer email.
I've checked these things and sure they 're configured correctly.
- validate email address, not have any special character.
- setting email in woocommerce properly.
- WP mail log has email was sent but the customer does not get any mail.

I've thought the problem maybe I have to configure something in the server ( LiteSpeed WebAdmin ) to sent mail.
Thank for any solution you have.