This article applies to:

• Trustwave MailMarshal (SEG)
• Trustwave ECM/MailMarshal Exchange 7.X

Symptoms:

Event ID: 3512
Type: Error
Source: MMEngine (MailMarshal SMTP) or MEXEngine (MailMarshal Exchange)
Description: Message unpacking error

Causes:

When MailMarshal receives a message, it breaks the message up into its individual components for analysis.

The event is raised whenever MailMarshal is unable to properly unpack a message into its constituent components.

More Info: 

As a security measure, if any component of the message cannot be properly extracted or analyzed, MailMarshal stops processing of the message and moves it to a "dead letter" folder. This action is taken to prevent potentially harmful content from being delivered.

For more information, see Q10868: What is a Deadletter?