Stop updating dns record
Some mailservers will not trust mail coming from your server unless they can do a reverse DNS lookup. Most mailservers care that a PTR record exists at all.
Strict mailservers do a forward lookup on the name your mailserver introduces itself as such as mail.example.com, verify it is the IP address that is read off the connection, and do a PTR lookup on that IP address to see if it resolves to the same name.
A very common mailserver that comes to mind is craigslist.
AOL is also famous for doing this check, and they have changed their minds from time to time and taken this check off, but it is impossible to predict when they will put the check back on again because they have several times in the past and still do sometimes.
This article attempts to put all the DNS considerations together into one document for your review.
Virtually all DNS Hosting Provider provide a web browser based control interface used to modify your DNS records, and should provide the technical support needed if you get stuck trying to modify any of the DNS records discussed in this article.
SPF gives other mailservers a way to verify that mail claiming to be from your domain is from one of your IP addresses.
You could point your NS records to another DNS hosting provider or to your own DNS server at your static IP address.
You still may need additional references to look up how to create them if you are not an expert with the DNS server you are managing.
However, this article is aimed primarily at readers who will be using a web based DNS hosting service with it's own technical support to help them if they need assistance with their DNS. It is very difficult to run a business with a dynamic home-user Internet plan.
Many companies, including your own ISP might offer DNS hosting on your behalf, but make sure they offer a web based interface which allows you to have some control over your DNS records and make sure they offer good technical support.
All of their interfaces are different, but they accomplish the same basic thing; they allow you to publish your hostnames and important DNS records such as the ones mentioned in this article to the Internet.