rplumber0.sharepoint.com is a Microsoft SharePoint subdomain, used by organizations for document management and collaboration. Unlike a typical e-commerce or service site, SharePoint instances are private workspaces accessed by employees or authorized partners. The redirect to login.microsoftonline.com is normal – it means the site requires authentication via Microsoft's identity platform.
So is rplumber0.sharepoint.com a scam? No. The security setup is solid: valid encryption, HTTPS enforcement, and protection against clickjacking. The domain is owned by Microsoft (via sharepoint.com), and the site appears on no blacklists.
What about the missing favicon and the robots.txt that blocks all crawlers? Those are standard for a private SharePoint site – you don't want search engines indexing internal content. If you're seeing this URL, it's likely because your organization uses it. Trust it as you would any Microsoft service.