How should I set up my PTR Record?

It does not matter what domain you're sending e-mail for. Explicitly, it does not matter what your employee's e-mail addresses are, it does not matter if they're [email protected]. I need to make that point 100% clear because everyone assumes it has something to do with this.

Now, your e-mail server has a hostname. For many companies it something like mail.example.com. This is what matters in regards to the PTR record. DNS for the mail server must match forward, backward, and with regards to the SMTP communications.

That means:

1. Your forward host name must resolve to the correct IP.
   mail.example.com must resolve to 1.1.1.1
2. Your reverse pointer must resolve to the correct host name.
   1.1.1.1 must point to mail.example.com
3. When your server connects to another server, it must connect from IP 1.1.1.1 and announce itself as mail.example.com (the HELO or EHLO message).

If you have more than one server they each get their own host name (eg mail1.example.com and mail2.example.com), and the above has to be true for each server.