IP Address: 2a01:111:f400:7e88::702

The address is registered to ORG-MA42-RIPE (UK-MICROSOFT-20060601), an enterprise network operator. Concentrated authentication failures on enterprise address space can indicate either a compromised internal host being used as an unauthorized sending relay, or an organization knowingly or unknowingly operating as a spam source.

Across the wider UK-MICROSOFT-20060601 network, 55 distinct IPs have been associated with 68 authentication failures over 73 observed messages, spanning 4 countries. Most observed IPs on this network contribute to the failure count, suggesting the range as a whole warrants elevated scrutiny.

For IPv6 addresses, per-address blocking provides minimal protection. Cloud providers and large networks typically allocate a full /64 prefix (containing approximately 18 quintillion addresses) to each customer. An attacker assigned a /64 can rotate through effectively unlimited addresses within the same prefix at no cost. Blocking should target the /48 or /64 prefix rather than the individual address.

If your domain appears in the From header of mail from this address, start with a misconfiguration investigation before assuming spoofing. Microsoft's infrastructure is used by many legitimate senders, and auth failures here most often reflect a broken SPF include chain, a DKIM signing gap on a shared sending path, or a forwarding rule that breaks alignment. Verify that your authorized senders on Microsoft are correctly publishing SPF and signing with DKIM before concluding the activity is malicious.

Your DMARC policy posture matters more than any IP-level response here. The enforcement action applied to this mail indicates your policy is already providing protection. Maintaining p=reject across all your domains closes the gap for attackers who manage partial alignment. Domains that remain at p=none long-term tend to be impersonated repeatedly, because the cost to the attacker of attempting is effectively zero.

Blocking this individual address has limited durability: an attacker can rotate to another address in the same /24 subnet at effectively zero cost. More durable responses include monitoring aggregate DMARC reports so new sources are visible as they emerge, tightening SPF to remove overly permissive include chains or +all mechanisms, and ensuring DKIM is signing every legitimate outbound stream so alignment failures are unambiguous. The formal abuse contact for ORG-MA42-RIPE is listed in ARIN WHOIS records, and timely remediation is achievable through that channel.