Empty messages are commonly used by spammers to perform directory harvesting. By default, messages with empty Subject and Body fields are treated as spam. However, legitimate users may wish to send short messages in the Subject field while leaving the body of the message empty. CSE provides the ability to specify how you wish to handle these messages.
How to configure options for empty messages
Open the Server Configuration window.
The General tab is displayed by default.
When you select “Treat empty messages as spam”, messages with empty Subject and Body fields are automatically treated as spam. This is the default configuration.
When you select “Treat messages with an empty body as spam”, messages with empty Body fields are treated as spam even if the Subject field is not empty. This option is not enabled by default.