If a ProxySG is configured to output eventlog messages via email, it is vitally important that the SMTP service configuration is correct.
For example,if the SMTP server configured is not configured to permit email relaying from the ProxySG appliance's IP address, the ProxySG will try 5 times to send an email, waiting 10 seconds between attempts. Each message takes 4 cache-blocks and remains in use until the message can be delivered. If the ProxySG appliance is not permitted to send the email per the mail server, then the SMTP message will fail. A failed message generates yet another message, and the cycle continues.
In the above scenario, with SMTP disabled, the allocated cache-blocks will eventually be returned. As the memory is released to the system, this is not a bug. However, if this configuration is not repaired, it will eventually utilize all system memory and result in the proxy entering a 'TCP acceptance regulation' scenario, where it will not accept further client requests due to a lack of memory.
In future documentation and release notes, this will be documented as a known issue. Blue Coat recommends that SMTP event logging configuration is confirmed as valid before committing it to a production proxy.