Dear , You have to find out which file is being reported by SMG . As a matter of fact , the XLSX format is itself a Zip file . I will suggest to rename the excel sheet to ZIP , extract the contacts and there you can find the file which is causing the Problem . Mostly its printer settings .
Check this article for more details .
https://www-secure.symantec.com/connect/forums/excel-files-xlsx-blocked-executable-files-sms-smtp-501