CaptivePortal.Nokia.com issue.

Greetings, marioblanca.

Welcome to the Apple Support Communities. It’s understandable that you’d want to resolve the issue with the error message appearing on your iPhone.

The error message you gave, leads us to think that something may not be correct in your Mail settings. Please confirm your settings: Mail - Official Apple Support

We hope this helps! Don’t hesitate to reach out with questions.

Sincerely.

When you use a public Wi-Fi network that requires login you are redirected to a captive portal to capture your login information. That portal is opened in Safari. After you are connected you should be redirected to the page you intended to go to. However, if you don’t go to that page the captive portal remains in your browser. It’s certificate expires a day later so the login is required the next day. So the next time you connect to that public network (or even get near it) you will get that error. There seems to be a problem with sites that are hosted with Nokia routers, and it’s probably a bug in the router software that doesn’t delete the page after connecting. I haven’t had the problem with any other captive portals.

Here’s Apple’s tech note on this→Use captive Wi-Fi networks on your iPhone, iPad, or iPod touch - Apple Support

One way to prevent this is to find the network in Settings/Wi-Fi when you are near it, tap on the i next to the name, and turn off Auto-join.

Open Safari, hold your finger on the overlapped squares at the bottom and choose Close all tabs.