A Microsoft Office 2007-formatted document may unexpectedly trigger a Content policy based on the attachment size in Symantec Messaging Gateway (SMG)
SMG 10.5.2 and previous look at all content within an XLSX document as it essentially works like a container. When the embedded content is larger than the set attachment size limit (though the overall attachment is not), this rule can trigger.
This behavior has been changed in SMG 10.5.3. For compliance rules, we no longer include the size of decompressed attachment data within an XLSX document.