Why, when sending mail with a return address containing Russian letters, unreadable characters appear instead of some of them?

Question

PHP

Sending mail via phpMailer:

$mail->From = "[email protected]имя-сайта.рф";
$mail->FromName = "Robot";
$mail->AddAddress($toEmail);
$mail->Subject  = $subject;
$mail->Body = $template;
$mail->IsHTML(true);
$mail->CharSet = 'UTF-8';
if(!$mail->Send()) {
// ...
}

Everything is sent and works fine, but in some mailers (for example, mail.ru) there is an incomprehensible problem: with the correct encoding of the entire letter, some letters from "site-name.rf" are not displayed. I would understand if the whole address was not displayed, but individual letters ... in the end it looks something like this:

Moreover, a mailbox with the same name was created on the hosting.
I don’t understand at all where to dig in this situation ... I will be grateful for any advice, thanks.
UPDATE
Solved the problem by writing Cyrillic in punycode.

Answer 1

I solved the problem by writing Cyrillic in punycode.

Answer 2

$email = "[email protected]имя-сайта.рф";
$send = mail ("Content-type:text/plain; charset = UTF-8\r\nFrom:$email");

...
something like this...