PHP Mail does not give an error, but letters do not come, why?

Question

PHP

Writes bool (true), but the letters do not come anywhere, yandex, gmail, mail.ru, nowhere.
The spam folder is empty.

<?php var_dump(mail("[email protected]","Test","Test")); ?>

There is no mail in php_disables
In php info sendmail is.

Answer 1

Look at the queue of letters on the server. Also, the mail server must be running, see its logs.
The fact that php generated a letter and put it in the spool does not mean that it will go away.