WordPress, emails from applications fall into the Spam folder

The site is on WordPress, the hosting and domain of the site are on REG.RU, the domain is Cyrillic. Requests from the feedback form are received, but for some reason they end up in the Spam folder.

I tried sending applications to the mail Mail.ru and Google, both of which were spam. PHP the handler used its own, placed it in the root of the installation WordPress, and provided the code below. I also tried sending via the plugin Contact Form 7, there are also spam emails.

I don't know what to do anymore, please tell me how to solve this problem?

<?php
header("Content-Type: text/html; charset=utf-8");
$name = htmlspecialchars($_POST["name"]);
$tel = htmlspecialchars($_POST["phone"]);
$email = htmlspecialchars($_POST["email"]);
$refferer = getenv('HTTP_REFERER');
$date = date("d.m.y"); // число.месяц.год
$time = date("H:i"); // часы:минуты:секунды
$myemail = "[email protected]";
$tema = "Новый заказ";
$message_to_myemail = "Уважаемый администратор, Вам поступил новый заказ
<br><br>
Имя: $name<br>
Телефон: $tel<br>
Источник (ссылка): $refferer<br>
";


mail( $myemail, $tema, $message_to_myemail, "Reply-To: Davydov-Event 
\r\n"."MIME-Version: 1.0\r\n"."Content-type: text/html; charset=utf-8\r\n" 
);


$tema = "Заказ принят";
$message_to_myemail = "
Спасибо, Ваш заказ успешно принят
";
$myemail = $email;
mail($myemail, $tema, $message_to_myemail, "From: Davydov-Event \r\n Reply- 
To: Davydov-Event \r\n"."MIME-Version: 1.0\r\n"."Content-type: text/html; charset=utf-8\r\n" );