Low Severity

Sender: Local part built from recipient domain and mailbox

Labels

BEC/Fraud
Credential Phishing
Spoofing
Evasion
Impersonation: Employee
Header analysis
Sender analysis

Description

Flags inbound messages where the sender's local part is constructed by combining the recipient's domain name and mailbox name (e.g., domain_mailbox). This pattern is commonly used to make the sender address appear related to or originating from the recipient's own organization, helping the message blend in and evade scrutiny.

References

No references.

Sublime Security
Created Aug 20th, 2026 • Last updated Aug 20th, 2026
Feed Source
Sublime Core Feed
Source
GitHub
type.inbound
and sender.email.local_part == strings.concat(recipients.to[0].email.domain.sld,
                                              '_',
                                              recipients.to[0].email.local_part
)
and sender.email.domain.root_domain != recipients.to[0].email.domain.root_domain
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