Public IP for Email recognized as Dynamic even though confirmed Static from ISP

[D!ABOL!C]

Hello Friends,

 

I want to keep the info protected, but I will provide enough info to see if you guys have any ideas on what can be done.

 

We have a customer that changed ISPs to Spectrum and have an Enterprise account with Static IP addresses. They have an internal exchange server which we have updated the MX records and everything and got mail flowing fine. We are still having issues with certain emails that are being blocked. What we have done to mitigate this is: We have created a Reverse PTR record through our ISP so that it says who they say the are. We have also created an SPF record to help with spoofing. After the cutover, the IP was on 2 black lists. After doing the Reverse PTR we were able to get removed from one black list. The other big blacklist as well as another one is saying the following:

 

Connections originating from dynamically assigned IP addresses are not allowed. Please use your ISP's relay servers

 

As I mentioned, this is an Enterprise account with a Static IP address. I tried contacting both of these mail hosts and no one is responding. I'm pretty much at a loss on what to do. These hosts are not responding and this is becoming an issue. The only option I can think of is to have our customer contact the individual emails that are issues and have them ask their IT people to whitelist. Any ideas on what other options I have? One of the blacklists the domain is on is SORBS Duhl. Thank you kindly!

Edited March 12, 2018 by D!ABOL!C

[+BudMan MVC]

What is the IP?  You would have to get with the owning ISP/Company to make sure the network they are handing out as "static" to customers is removed from the dynamic listing..

 

http://www.sorbs.net/faq/dul.shtml

 

Requests for entries to be added to or removed from the SORBS DUHL can be made by any Internet service provider responsible for a particular range of IP addresses.