This indicates an attack attempt to exploit a Buffer Overflow vulnerability in Ipswitch IMail server.
The vulnerability is due to an improper boundary check condition in the application when handling an overly long SMTP command. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application.
Ipswitch IMail Server 2006 prior to 2006.04a
Ipswitch IMail Server Plus 2006 prior to 2006.04a
Ipswitch IMail Server Secure 2006 prior to 2006.04a
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.