Sh4mefulIP Address: 185.58.87.43 ⚠ Network Confounder
Mimecast is a cloud-based email security gateway that enterprises route all inbound and outbound corporate email through for spam filtering, malware scanning, URL click-protection, and archiving. It breaks DKIM authentication by modifying message bodies during inline security processing — URL rewriting and footer insertion invalidate the original DKIM body hash. On the SPF side, Mimecast relay IPs become the actual sending IPs, breaking SPF alignment unless the domain owner has explicitly included Mimecast netblocks in their SPF record and enabled SPF alignment in the Mimecast admin console. DMARC failures originating from Mimecast IP ranges are almost always legitimate corporate email with a configuration gap, not spoofing or spam attempts.
This page shows DMARC authentication failure data for this IP address. Learn more about this data.
Geolocation Information
- Country:
- GB United Kingdom
- Coordinates:
- 51.4964, -0.1224
WHOIS Information
- Network Name:
- UK-MIMECAST-NET3
- CIDR:
185.58.87.0/24- Owner:
- ORG-MSL21-RIPE
- Reverse DNS:
-
eu-smtp-delivery-43.mimecast.com
Last updated: 2/5/2026
Analysis
This IP was first observed on March 13, 2024 and most recently on April 30, 2025. It has been associated with 4 failed authentication events affecting 4 messages, representing low but recurring activity. The IP belongs to UK-MIMECAST-NET3 (ORG-MSL21-RIPE), a network with activity associated with United Kingdom. One other IP in the same /24 subnet (185.58.87.*) also appears in this dataset.
External Reputation Lookups
Look up this IP in external threat intelligence and reputation databases (opens in new tab):
Nearby IPs
Other IPs in the 185.58.87.0/24 range observed failing DMARC:
185.58.87.41 (1 failure)