domain name system - Reverse dns how to setup ptr record?

For my own mailserver I now have to setup PTR records for the reverse DNS.

My question is in which fields do I put what?
For example my IP address is 192.168.4.4 and domain example.com (with mailserver mail.example.com)

Name: ?
Type: PTR

Value: ?

Do I also have to update the spf record?

Answer

62    IN    PTR    mail.mydomain.com.

Further you don't have to update the SPF record since its contained in the forward lookup zone. Adding a PTR record happens in the reverse lookup zone (55.234.123.IN-ADDR.ARPA.) thus it not affects the other zone.