Send mails through SMTP without plugin

functions.php

add_action('phpmailer_init','send_smtp_email');
function send_smtp_email( $phpmailer )
{
    // Define that we are sending with SMTP
    $phpmailer->isSMTP();
 
    // The hostname of the mail server
    $phpmailer->Host = "smtp.example.com";
 
    // Use SMTP authentication (true|false)
    $phpmailer->SMTPAuth = true;
 
    // SMTP port number - likely to be 25, 465 or 587
    $phpmailer->Port = "587";
 
    // Username to use for SMTP authentication
    $phpmailer->Username = "yourusername";
 
    // Password to use for SMTP authentication
    $phpmailer->Password = "yourpassword";
 
    // The encryption system to use - ssl (deprecated) or tls
    $phpmailer->SMTPSecure = "tls";
 
    $phpmailer->From = "your-email-address";
    $phpmailer->FromName = "Your Name";
}