This indicates an attempt to exploit a vulnerability in MERCUR Messaging 2005.
The vulnerability is a stack-based buffer overflow in the IMAP service. A remote attacker can cause a buffer overflow by sending a long string to the LOGIN or SELECT command. As a result, the attacker may be able to cause a denial of service or may execute arbitrary code.
Atrium Software MERCUR Messaging 2005 Standard Edition 5.0 SP3
Atrium Software MERCUR Messaging 2005 Lite Edition 5.0 SP3
Atrium Software MERCUR Messaging 2005 Enterprise Edition 5.0 SP3
System Compromise: Remote attackers can gain control of vulnerable systems.
Denial of Service: Remote attackers can crash vulnerable systems.
Update to MERCUR Messaging 2005 - SERVICE PACK 4.