lokey6475
When sending mail from the platform by default we use PHP Mail function. It is recommended that you go to the Email (Admin Panel > Emails > Emails > click the email), click Outgoing (SMTP) tab, configure the SMTP server information, and Save Changes. Once SMTP is configured successfully outgoing mail will be sent through your mail server and ensure the best possible deliverability.
However if you cannot configure SMTP and must use PHP Mail then you can follow PHP's documentation on how to configure it properly.
Cheers.