Hi Abdul,
Attachments stripped by content filters cannot be retrieved.
You could try using message filters instead with an additional archive action.
The archive action saves a copy of the original message, including all message headers and recipients into an mbox-format file on the appliance.
Achive action is explained in the end user guide Page 9-71.
www.cisco.com/c/dam/en/us/td/docs/security/esa/esa9-7/ESA_9-7_User_Guide.pdf
Thank You!
Libin Varghese