Hello Sharif Bouali,
Thank you for posting in Microsoft Community.
Based on your description, when you click a link on Outlook, you go to a browser and are then asked to sign in, and then you can view the page. feel free to correct me if I misunderstood.
To appropriately assist you, we need some more details:
What kind of outlook are you using? classic outlook or new outlook?
What version of Outlook are you using? you can find details on What version of Outlook do I have? | Microsoft Support
Are you using Exchange Online, aka Office 365?
Are you using any kind of email security? such as Microsoft Defender for Office 365? Proof Point, Avanan, FortiMail...?
Does this issue happen when you click the link while you are on Outlook on the web?
Do links open in the default browser?
If you are using Microsoft Defender for Office 365, you need to check with your IT administration about Set up Safe Links policies in Microsoft Defender for Office 365 | Microsoft Learn. Policies can be set up to mimic the scenario you are describing.
Your prompt response is essential to provide the right assistance.
Best regards,
Microsoft Community