rdns help for mail server

I have a mail server say "a record and ehlo = server1.example.com" and would like to know if I should have my rdns point to "server1.example.com" or "example.com" as the domain name in rdns ?

Thanks in advance for any info on this.

 

That doesn't matter as long as both example.com and server1.example.com are pointing to that IP address.

 

thanks falko