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OSSEC / HIDS Rule 3355

OSSEC / HIDS rule catalog

  • Rule family: OSSEC / HIDS
  • Rule ID: 3355
  • Definition status: Present in current source
  • Alert message / subject: Postfix: Multiple attempts to send e-mail to invalid recipient or from unknown sender domain.
  • Rule level: 10
  • Definition checked: 2026-10-21
  • Configured frequency: $POSTFIX_FREQ
  • Timeframe (seconds): 120
  • Ignore interval (seconds): 60

Correlation values are configuration attributes; event-count behavior depends on the manager version and parent rules.

Interpretation and response

This event is recorded as “Postfix: Multiple attempts to send e-mail to invalid recipient or from unknown sender domain.” Review the originating log and the affected host or service to determine whether the activity was expected.

An OSSEC/HIDS event records or correlates activity. Blocking depends on the originating application and any separately configured Active Response policy; an alert alone does not prove that an attack was blocked.

Documentation

The following guidance was migrated from the historical wiki and reviewed against the rule definition. Legacy ASL product names and interface instructions refer to the versions documented then. Use the current metadata above and your installed configuration when interpreting thresholds, notification settings and response behavior.

Description

Postfix: Multiple attempts to send e-mail to invalid recipient or from unknown sender domain. 10 / 120s

What you should do

No actions recommended

Troubleshooting

False Positives

A legitimate event may still trigger this rule. Review the surrounding activity before deciding whether it is malicious.

Tuning Guidance

There is no guidance for tuning this rule, this is a generic error and the rule should not be disabled.

Additional Information

Support

If you are unsure about how to respond to this alert, please contact Atomicorp support. We’re here to help you!

Source and revision

Migrated from HIDS_3355, wiki page 891, revision 6257 (20201023). Documentation review: 2026-10-21. An archived wiki status of Active is not a current deployment status.

For assistance, provide the rule ID, installed product and rule version, and a sanitized event to Atomicorp support .