This topic

BT DNS returns NXDOMAIN for our business domain - all BT customers affected, works on every other IS

briantruongau — Wed, 02 Sep 2026 09:18:55 GMT

Hi all,

Hoping a moderator can help escalate this one, as it's costing us customers.

Our web app at builder.printerp.ai cannot be reached by any of our customers on BT broadband. On every other UK ISP — and on any public DNS — it loads fine. We've confirmed this across multiple separate BT customers on different BT lines.

BT's DNS returns "Non-existent domain":

C:\> nslookup builder.printerp.ai
Server:  hub.home.arpa
Address: 192.168.1.254

*** hub.home.arpa can't find builder.printerp.ai: Non-existent domain

This isn't a caching issue — customers have flushed DNS and rebooted their hubs repeatedly over several days with no change.

Here's the part that makes me think it's a filtering false positive:

Other hostnames in the exact same DNS zone resolve perfectly on the same BT connection, at the same moment, returning identical IP addresses:

api.printerp.ai            104.21.66.237, 172.67.165.220   -> resolves OK
builder.printerp.ai        104.21.66.237, 172.67.165.220   -> NXDOMAIN

Same nameservers, same IPs, same zone. Only that one hostname fails, and only on BT. If a customer sets their DNS to 8.8.8.8 it works instantly — so this is happening at BT's resolvers, not in our DNS config.

For what it's worth, the domain is clean everywhere I've checked:

Google Safe Browsing — "No unsafe content found"
Spamhaus — "no issues"
Netcraft — no fraud or malware indicators

We're a legitimate B2B business — the site is a tool UK print and apparel companies use to prepare artwork and manage print orders. We're BT Business customers ourselves.

I've emailed saferbrowsing@bt.com as well, but posting here in case a moderator can help move it along.

Is there anything else I can provide to get this looked at?

Thanks.

Re: BT DNS returns NXDOMAIN for our business domain - all BT customers affected, works on every othe

imjolly — Wed, 02 Sep 2026 09:24:06 GMT

this is a residential customer help customer forum and as business user you need to post here

https://business.forums.bt.com/

Re: BT DNS returns NXDOMAIN for our business domain - all BT customers affected, works on every othe

briantruongau — Wed, 02 Sep 2026 09:27:39 GMT

Many thanks for your information.

Re: BT DNS returns NXDOMAIN for our business domain - all BT customers affected, works on every othe

bobpullen — Fri, 04 Sep 2026 22:49:16 GMT

Would be useful to understand what DNS server your affected customers' routers are using. If I query one of the BT DNS server IPs it looks good from where I'm sat: -

~$ dig builder.printerp.ai @81.139.56.100 ; <<>> DiG 9.18.39-0ubuntu0.22.04.4-Ubuntu <<>> builder.printerp.ai @81.139.56.100 ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 15937 ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 1232 ;; QUESTION SECTION: ;builder.printerp.ai. IN A ;; ANSWER SECTION: builder.printerp.ai. 300 IN A 104.21.66.237 builder.printerp.ai. 300 IN A 172.67.165.220

Re: BT DNS returns NXDOMAIN for our business domain - all BT customers affected, works on every othe

briantruongau — Mon, 07 Sep 2026 10:37:32 GMT

@bobpullen — thanks, here's the data you asked for.

An affected customer on a BT line, after a DNS flush:

C:\> nslookup builder.printerp.ai
Server:  hub.home.arpa
Address: 192.168.1.254

*** hub.home.arpa can't find builder.printerp.ai: Non-existent domain

The resolver serving that line:

C:\> nslookup -type=txt o-o.myaddr.l.google.com
o-o.myaddr.l.google.com text = "81.134.101.38"

Querying that same IP from outside the BT network:

$ dig builder.printerp.ai @81.134.101.38
;; ->>HEADER<<- opcode: QUERY, status: NOERROR
builder.printerp.ai. 300 IN A 172.67.165.220
builder.printerp.ai. 300 IN A 104.21.66.237

Both published resolvers also answer correctly for me:

$ dig builder.printerp.ai @81.139.56.100  → NOERROR, 172.67.165.220 / 104.21.66.237
$ dig builder.printerp.ai @81.139.57.100  → NOERROR, 172.67.165.220 / 104.21.66.237

Other hostnames in the same zone resolve fine on the same BT line at the same time, returning identical IPs:

api.printerp.ai            → resolves
builder-stage.printerp.ai  → resolves
app.printerp.ai            → resolves
builder.printerp.ai        → NXDOMAIN

I'll leave the interpretation to BT. What I can say is the domain is clean on Google Safe Browsing, Spamhaus and Netcraft, and it resolves normally on every other UK ISP.

I've emailed saferbrowsing@bt.com three times (2, 3 and 4 September) with no reply, no acknowledgement and no case reference. BT Business live chat couldn't raise one either. @BethM pointed me to that address and I've followed it exactly.

Is there another route to someone who can look at this? Happy to provide anything else that helps. My pleasure.