Sh4meful DMARC Spoof Detection
IP Address: 40.107.243.110
Differentiating between Office 365, including email protection services, and Azure (public cloud) when diagnosing incidents is challenging because they utilize shared Microsoft-owned IP ranges. Most of this is probably O365/Outlook or Defender protection breaking DKIM and SPF authentication. Disambiguation is a work-in-progress.
About this Data
▶The data here is from DMARC analysis for domains I administer, drawn from a larger dataset (comprising millions of authentication records and messages). These entries are from email attempts that failed both SPF and DKIM (and there are often alignment issues - hidden here). In many cases, these failures indicate unauthorized use of the domain name, and are commonly associated with spoofing, phishing, or other abusive mail activity.
Geolocation Information
- Country:
- US United States
- Region:
- Iowa
- City:
- Des Moines
- Coordinates:
- 41.6015, -93.6127
WHOIS Information
- Network Name:
- MSFT
- CIDR:
40.125.0.0/17, 40.124.0.0/16, 40.112.0.0/13, 40.74.0.0/15, 40.76.0.0/14, 40.96.0.0/12, 40.120.0.0/14, 40.80.0.0/12- Reverse DNS:
-
mail-dm6nam12on2110.outbound.protection.outlook.com
Last updated: 2/5/2026