Good morning my name is Julio César Azcanio, I’m a cloud architect with specializations in Google Cloud, AWS and Azure.
Currently I offer remote technical support to various companies around the world.
I manage various Plesk Panel with the same problem for more than 40 companies around the world, the problem lies in the lack of various policies. If you plan to send many emails through Wordpress or Outlook we must solve it through an Email Relay Server.
I need SSH access to your Plesk instance and I can install the relay server to send up to 12,000 emails per month for free. I assure you that all emails will go directly to the inbox.