Google Message Security for Google Apps Administration Guide - Manual (Page 204)

204 Message Security for Google Apps Administration Guide
Types of Content Scanned
In any part of an email message, Content Manager scans the text-based or HTML
content, as well as any MIME (base-64) sections for binary attachments (the
sections that usually appear as “gibberish” in the message source). If you choose
the option to scan the entire message, Content Manager also decodes and then
scans sections in MIME and quoted-printable encoding (for non-ASCII text). In
this case, Content Manager also scans the actual text content of binary
attachments.
When Content Scanning Occurs
Content Manager scans all information transmitted during the DATA phase of an
SMTP session. It does not scan sender or recipient content transmitted during the
MAIL FROM or RCPT TO phase of an SMTP session.
How Quickly Content Scanning Occurs
Content Manager takes just milliseconds to scan a message according to all
content rules and then execute the disposition of any filter that captures it.
Therefore, the use of Content Manager does not affect the speed at which the
message security service processes your email.
Attachments That Content Manager Scans
When you create a content filter, you can choose to scan any part of a message or
all parts of a message. If you select the Body option for a filter rule, Content
Manager also scans any plain-text attachments. If you select the Entire Message
option, Content Manager scans text-based content in many types of file
attachments, including:
• Text files
• HTML files
• Documents created with Microsoft Office 2003 or earlier versions (Word,
PowerPoint, and Excel)
• Forwarded email messages
• Various types of other files with text-based content
Note: For binary file attachments, such as Microsoft Office documents, Content
Manager decodes and then scans the MIME (base-64 encoded) parts of the email
message.