Which result in an email exchange indicates a possibility of unauthorized IP addresses sending emails on behalf of the domain?

The indication of a "Received-SPF: Softfail" result is significant in identifying a potential issue with unauthorized IP addresses sending emails on behalf of a domain.

When the Sender Policy Framework (SPF) is used to validate whether an email is sent from an authorized IP address, a softfail result suggests that the email is sent from a server not listed as an authorized sender in the domain’s SPF record. This indicates that the message may not have originated from a legitimate source, but the SPF policy is set to a less strict stance, meaning it doesn't outright reject the email but flags it for further scrutiny.

The presence of a softfail can be caused by legitimate reasons, such as misconfigured SPF records or transitional configurations, but it significantly raises the risk of abuse since it allows emails from unauthorized sources through while warning the recipients. This is crucial in digital forensics as it may lead to investigating whether the given IP addresses or third-party email services are being misused to send emails pretending to be from a trusted domain.

Other results, like a pass or none, either denote clearly authorized sending or no SPF validation taking place, which do not raise the same level of concern regarding unauthorized transmissions. A fail indicates an outright rejection from unauthorized sources,