where must a PTR record point to in order to avoid being classified as spammers?

Question

I could not find a definitive answer to this question online and I'd appreciate some help.

We have a dedicated server for our website. We also use it to send out bulk emails (ALWAYS by request, NEVER unsolicited or spam). We are trying to set up a PTR record and there's one thing I simply can't understand:

If I send out email from someone@example.com, and example.com's A record is x.x.x.x, then in order for my IP not to be considered a spammer, the PTR record for x.x.x.x must point to:

1. example.com?
2. any of example.com's MX records?
3. the name of the domain as it appears in the SMTP banner you receive when connecting to example.com:25?
4. all/none/any of the above?

Thanks for helping out!

Answer 1

The name provided as a response to HELO/EHLO should be resolvable to the sending server's IP address (A/CNAME record) and it's IP address should be resolvable to the name provided in response to HELO/EHLO.

You should NEVER create a PTR record, whose result could not be resolved to the original IP address.

If your sending mail server is not one of your MX records (or the domain in your HELO/EHLO response does not match your mail domain example.com), you may provide an additional SPF record for example.com (see Sender Policy Framework at Wikipedia).