spamBlocker scans each file up to a specified kilobyte count. Any additional bytes in the file are not scanned. This allows the proxy to partially scan very large files without a large effect on performance.
The default scan limit for spamBlocker is 100 KB for all devices except the Firebox T15, which has a default scan limit of 60 KB. For the SMTP and POP3 proxies, the Firebox sends the first 100 KB of the message body for scoring. For the IMAP-proxy, the Firebox sends all of the message up to the scan limit.
The minimum scan limit is 1 KB for all Firebox models. The maximum scan limit is 2000 KB for all devices except the Firebox T15 which has a maximum scan limit of 1000 KB.