IP Address: 40.107.43.23 ⚠ IP Confounder

⚠ IP Confounder Detected: Microsoft 365 Exchange Online Protection (EOP)
Outbound; PTR: *.outbound.protection.outlook.com

ℹ️ Network Annotation: Microsoft Network (365 vs Azure)

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.

Last updated: 1/29/2026

This page shows DMARC authentication failure data for this IP address. Learn more about this data.

Geolocation Information

Country:: KR South Korea
Region:: Seoul
City:: Seoul
Coordinates:: 37.5658, 126.978

WHOIS Information

Network Name:: MSFT
CIDR:: 40.120.0.0/14, 40.112.0.0/13, 40.124.0.0/16, 40.74.0.0/15, 40.76.0.0/14, 40.96.0.0/12, 40.125.0.0/17, 40.80.0.0/12
Owner:: Microsoft Corporation
Org ID:: MSFT
Address:: One Microsoft Way, Redmond, WA 98052
Reverse DNS:: mail-koreacentralazon11012023.outbound.protection.outlook.com
Last updated: 2/5/2026

Analysis

This IP was observed on a single date: June 26, 2025. It has been associated with 1 failed authentication event affecting 1 message — a single isolated event. The IP belongs to MSFT (Microsoft Corporation), a network with activity associated with South Korea. One other IP in the same /24 subnet (40.107.43.*) also appears in this dataset.

Failures Detected from this IP

Showing 1-1 of 1 failures, affecting 1 message

Date ▼	Messages
6/26/2025	1

External Reputation Lookups

Look up this IP in external threat intelligence and reputation databases (opens in new tab):

AbuseIPDB Cisco Talos Project Honey Pot GreyNoise VirusTotal Shodan Censys Spamhaus

Nearby IPs

Other IPs in the 40.107.43.0/24 range observed failing DMARC:

40.107.43.48 (1 failure)