From Symantec :- Disabling email protection does not leave you
vulnerable to viruses and malicious software in email. It is a separate
layer of protection in addition to Auto-Protect. Auto-Protect scans any
incoming files, including email, as they are saved to your hard drive.
As long as you keep your virus definitions up to date with LiveUpdate,
and keep Auto-Protect enabled and set to scan files as they are created
or downloaded, your system is fully protected.
Without email protection enabled, your email program connects directly
to the mail server and downloads the mail. Email protection creates a
step in between; it sets up a proxy server on your computer. Your email
program connects to the proxy server, rather than the mail server; the
proxy server then connects to the mail server, downloads the mail, and
scans it for viruses. Then, and only then, does your email program
receive the email. (This causes problems for lots of users, who are then
unable to receive their mail.)
Any AV program worth it's salt should kick in whenever you attempt to
open and infected file.
Kath