How solve ERROR: No reverse DNS (PTR) entries. The error MX records are:

As you have a dynamic address configure your email server to relay all mail via your ISP's relay server. By far the majority of spam originates from dynamic addresses without a PTR record. If you try to send email directly you will appear to be a spammer. This is why your attempt to send are failing.

If you want to send email directly get a static IP address. You will need to get the PTR record configured by whoever supplies it. The PTR should point to a domain which has an A record for the static IP address.

To answer your new question first: No, PTRs don't tell you anything about the sender's domain. See below for the explanation.

Now back to your original question:

Receiving mail servers check none, one, many or all of the following:

1. Is the HELO name equal to the hostname (A record)?
2. Is PTR of the IP equal to the A record of the hostname (hostname ==(PTR)==> IP ==(A)==> hostname)?
3. Is the IP part of the provided SPF record?
4. Does the sender's domain have at least one MX record? Which doesn't have to match IP/hostname.

Receiving mail servers that check if the sending server is also the MX server are badly configured and should be eliminated from the Internet.

Edit: The PTR does absolutely prove nothing about the email domain. It is never meant to prove this. There are thousands of domains hosted at Google, Amazon, AOL and others. But none of them match the hostname or PTR of Google, Amazon, AOL and others. They all have the servernames of the providers. And there is nothing bad about that.

The PTR only proves the identity of the server but not the identity of the hosted domains. Point.

2nd Edit: A good example for a working environment would be

• HELO = mail.example.com
• hostname = mail.example.com
• A record of mail.example.com = 172.20.25.25
• PTR of 172.20.25.25 = mail.example.com
• Domains hosted on this server/system = example.com, *.example.com, *.example.net, *.example.org, mycompany.invalid and many many more.
• SPF records of hosted domains (optionally) = v=spf1 a:mail.example.com -all
• MX record of hosted domains can be anything. E.g. mx1.example.com, mx2.example.com, mailfilter.anti-spam-corp.invalid, mail.example.com, postini.google.invalid, ...