DNS has been a very confusing topic for me

Anyhow I have a server with hostname server.abc.com and IP The host names I setup on registrar for this abc.com are ns1.abc.com, ns2.abc.com

My site domain is xyz.com and I changed the nameservers of this domain to ns1.abc.com and ns2.abc.com

Now IP is also the dedicated IP of my site xyz.com i.e. if I enter this IP in browser, it opens my site xyz.com.

Now hotmail is sending my mails in JUNK. I noticed that rDNS of my IP is pointing to some third party server (ppp.oooo.com)

I have to correct the reverse-DNS

Now should I set the reverse-DNS for my IP to my server hostname (server.abc.com) OR my site's domain name (xyz.com).

Btw email header of hotmail says:

Received: from server.abc.com ([]) by SNT0-MC3-F41.Snt0.hotmail.com with Microsoft...........
Now I feel the reverse-DNS for my IP should point to my hostname i.e. server.abc.com but then I also fear that doing this would then point my IP ( to server.abc.com, instead of my site xyz.com (like I mentioned earlier if I enter this IP in browser, it opens my site xyz.com).

I am confused like hell. Please suggest if I should do use the hostname (server.abc.com) OR my site’s domain name (xyz.com) for reverse-DNS.

Thanks in advance.