Issue with AT&T IPs?

[Lightner, Jeffrey]

We're having issues send email to a user @SIDDHAFLOWERS.COM

Investigation here shows that the issue we have is querying your name servers (both by name and by IP) are refusing to respond to our name servers.

Their name servers:
NS1.QUICKFIX8.COM
NS2.QUICKFIX8.COM

Our name servers:
DSWADNS1.WATER.COM
DSWADNS2.WATER.COM

We find other name servers such as those as Google are able to query their name servers.   Based on that I determined their name server IP (for both) is 74.124.202.236.   However, if I attempt to reach port 53 (DNS) on that IP from our name servers it simply fails to connect.   Our Network Security engineer did a capture and shows we send packets but never get a response.

Interestingly further testing shows this is an issue from any of our AT&T provided IPs:
12.44.84.194
12.44.84.213
12.44.84.214
12.44.84.216
But not from separate QTS Datacenter provided IPs:
209.10.103.136
209.10.103.148

I've reached out to the folks at QuickFix and am waiting to hear back but we've seen a similar issue on another domain using separate name servers.    Is it possible there is some sort of blacklist for DNS (not email) that people might be subscribing to that would cause them to block AT&T IPs?  We can do queries from our DNS to most domains but have identified these 2 as problems so suspect there might be others.

By the way, I can reach their mail server via command line connection to port 25 on its IP.   The issue here is purely in querying the DNS servers which of course means mail programs can't determine the MX records themselves.

Last night I did see some posts suggesting commenting out query-source but testing that didn't do anything.   We do have our query-source setup for random outbound ports and I verified last night that it still works based on the test site for that.

Most of what I find about blacklisting is about spam blacklisting of mail servers not blacklisting of DNS server queries and it is the latter we are experiencing.


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