Why is RSForm not sending emails?

Question

Joomla

Good afternoon.
There is Joomla 3.1 and a feedback form made on RSForm. Emails are sent without SMTP authentication, the standard "mail" function is used.
When sending, everything works without problems, it does not give errors, but the letter to the site administrator does not come.
Perhaps someone faced this problem, I would be grateful for the "tip".