Event ID - 4188

Event Id4188
DescriptionRefused to relay <message details>
Event InformationMessage details: "<email address> for xxx.xxxx.net.xx(<ip number>)" - From a newsgroup post: "If the exchange server is behind a PIX firewall check the PIX smtp handling - If its enabled, it kills the auth login every time, so external clients cant send through the server even if they are set to authenticate."
Its also saying that , if a spammer trying to use a open relay on exchange server to send mail, this error may occurred. It means a client which is unable to authenticated by server is trying to send mail.
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