From eScan Wiki
Q. How does eScan scan my emails?
A. eScan includes a component called 'MailScan-Lite' to Scan your emails.
MailScan-Lite will break the mails into 2 parts i.e the body & the attachment. After the disassembly, the body is checked for restricted contents & attachments are scanned for viruses.
After this is done, the email is once again assembled and forwarded to your Inbox.