Why can the mail (php) function normally send a message to one address, and not send it to another?

Question

PHP

Good day. There was a following problem. There is a site that, for example, we will call mysite.com. Lies on a normal hosting. This domain was connected to Yandex mail. To a box like [email protected], if you just send a message from another mail, letters reach. From the site, using the mail function, I send a letter to two mailboxes: [email protected] and hello @yandex.ru . And for some reason, letters constantly reach the second (hello @yandex .ru) normally, but they don’t come to the first ([email protected]) (Tell me, what could be the problem?

Answer 1

Most likely the hosting mail server thinks that the mail is intended for him. Perhaps in the control panel you can disable mail processing. It is also worth looking at what's going on with DNS (if not the hoster's DNS is used) and either indicate that the zone is serviced by another server, or specify the correct MX records.
It will be easier to contact support (=

Answer 2

Contact your host. Sending mail to specific services often dies

Answer 3

Write to the hosting support to check the responses of the recipient's servers in the logs. You can guess as much as you like, only the logs will tell you what's wrong.