safelinks.protection.outlook.com
Microsoft Safe Links (Outlook)
What it is
Microsoft Defender for Office 365 rewrites links in incoming email to https://<datacenter>.safelinks.protection.outlook.com/... and checks each one when it's clicked before sending the reader on. The prefix, like nam01 or eur03, is the datacenter.
Why there's no full URL
When this shows up as the referrer, the visitor came through Microsoft's checking step, not from a web page, so there's no source page to report. Microsoft doesn't document what referrer the redirect passes on.
What traffic it represents
Clicks on links to your site in emails received by organizations that use Defender for Office 365 Safe Links, often newsletter clicks from business readers.
Sources
Scanned URLs are rewritten or wrapped using the Microsoft standard URL prefix: https://<DataCenterLocation>.safelinks.protection.outlook.com
Complete Safe Links overview for Microsoft Defender for Office 365
If a users clicks a rewritten link, it's scanned for malicious content before directing the user to the page.
Complete Safe Links overview for Microsoft Defender for Office 365
Related referrers
android-app://com.google.android.gmGmail app on Androidmail.google.comGmail on the web
Referrers, grouped by how people arrived
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