SMPT for woocommerce order invoices
So the interesting thing it is possible to activate SMTP sending for newsletters.
However while activated if you send to your customers an order invoice or order comment then PHP mail is used and not the SMTP route even while SMTP route is enabled for newsletter sending in mailpoet.
Would be awesome if mailpoet team will fix it.
To install simply another additional SMTP addon creates a conflict and is not a solution