Orange Poland cannot reach SegmentParty custom domain, vercel.app works

Hello,

Our Vercel project `segmentparty` is reachable through its Vercel deployment domain, but users on Orange Poland cannot reach either custom domain:

- https://segmentparty.com

- https://www.segmentparty.com

The issue reproduces on both Orange LTE and Orange fibre Wi-Fi from multiple devices in different locations. The Vercel deployment URL works from those exact networks and devices. The same custom domains work from another network providers.

Evidence:

- Current V4 diagnostic page: https://netstat.okstudio.pl

- Independent V4 health check: https://netstat.okstudio.pl/health.json

- Orange LTE: test ID ebb79fa0-08df-4ffe-8f9f-a0b52eec79dc, 2026-08-11T08:23:39.770Z UTC; custom domains fail in ~85 ms,

Vercel deployment responds in 497 ms.

- Orange fibre: test ID 5d13deda-3532-4c73-a98b-68e1e0b1cb7a, 2026-08-11T08:25:24.347Z UTC; custom domains fail in ~25 ms, Vercel deployment responds in 331 ms.

- Toya Wi-Fi: test ID 733ce40f-eef9-4bea-8858-20deb1a17a20; both custom domains are reachable.

The domain is delegated to ns1.vercel-dns.com and ns2.vercel-dns.com and is shown as attached to the correct project. Public DNS returns the Vercel addresses listed in the attached diagnostic report. There is no AAAA record.

Could you check whether Orange Poland has a routing, peering, Anycast, edge, or IP-reachability issue to the Vercel addresses selected for this custom domain? Please also check whether requests from the two Orange timestamps reached the Vercel edge. If they did not, this is likely upstream of the application and should be investigated by the networking/edge team.

We are not requesting an application code or database investigation at this stage.

The domain troubleshooting guide can help with most custom domain configuration issues. You might be able to use that guide to solve it before a human is available to help you. Then you can come back here and share the answer for bonus points.

https://vercel.com/docs/domains/troubleshooting

vercel.com

Troubleshooting domains

Learn about common reasons for domain misconfigurations and how to troubleshoot your domain on Vercel.

Resolved.

After I contacted Orange Poland’s CERT team and reported the issue, they intervened and the problem was resolved. segmentparty.com is now reachable normally from Orange networks.

Unfortunately, Orange did not provide any explanation of what caused the issue or what was changed to fix it.

Given that the problem disappeared following my report and Orange’s intervention, it appears the issue was entirely on the Orange side rather than with Vercel or our application. The exact root cause remains unknown.