Check IP reputation.
The address of the server your mail leaves from decides its fate as much as DNS records do. I check six lists and the reverse record many receivers refuse mail without.
What to fix, in this order
Nothing to fix in this check.
Before you ask.
Which IP address should I enter?
The server your store mail leaves from: the site hosting (if the store sends via PHP) or the SMTP server from the plugin. You find it in the "Received" header of a sent message or in the hosting panel.
What is PTR?
The reverse record that maps an IP address back to a server name. Mail servers check it on every connection; a missing PTR is one of the most common reasons mail from small servers is refused.
Would you rather have meset it up and watch it?
WooCommerce store support plans from 1,200 PLN net per month, no minimum term. For a 20-minute call I keep two fixed slots: Tuesday and Thursday, 18:00-19:00 CET.