Core issue
This problem occurs due to the presence of Cisco bug ID CSCse47150.
The PIX Firewall/Cisco Adaptive Security Appliance (ASA) running software version 7.2.1 can crash with the Thread name Dispatch Unit error when the Extended Simple Mail Transfer Protocol (ESMTP) inspection engine is enabled.
This problem occurs when the data length for segmented packets are miscalculated.
Resolution
As a workaround for this issue, perform either of these steps:
- Disable the ESMTP inspection engine.
Refer to the inspect esmtp command for more details.
- Download and upgrade the software version to any of these:
Product Family
Firewall - PIX 500 series
PIX Software Version
PIX version 7.x