A PTR record answers “what name does this IP claim?” — the reverse of normal resolution. Receiving mail servers verify that the sending IP’s PTR exists and resolves back consistently (FCrDNS); missing or mismatched reverse DNS is a strong spam signal.
PTR records are controlled by whoever owns the IP — your hosting provider — not by your domain’s DNS. On shared servers the PTR points at the server’s hostname, which is correct and expected: it must match what the mail service announces in its HELO, not your individual domain.
Frequently asked questions
Should the PTR match my domain name?
No — it must match the mail server’s hostname (its HELO name). On a shared server hosting fifty domains, that is the server’s name, not any one customer domain.
How do I change a PTR record?
Through your hosting/IP provider — reverse zones belong to the IP owner. On managed servers it is usually already set correctly.