Thanks for your reply, but when i searched on the Zimbra.log file i found this error:
(00975-02) ClamAV-clamd: Can't connect to INET socket 127.0.0.1:3310: Connection refused, retrying (1)
and in the freshclam.log file:
freshclam daemon 0.95.1-broken-compiler (OS: linux-gnu, ARCH: i386, CPU: i686)
ClamAV update process started at Thu Feb 3 13:07:01 2011
WARNING: Your ClamAV installation is OUTDATED!
WARNING: Local version: 0.95.1 Recommended version: 0.96.5
DON'T PANIC! Read
http://www.clamav.net/support/faq
main.cvd is up to date (version: 53, sigs: 846214, f-level: 53, builder: sven)
Trying host db.us.clamav.net (65.19.179.67)...
WARNING: getfile: daily-12529.cdiff not found on remote server (IP: 65.19.179.67)
WARNING: getpatch: Can't download daily-12529.cdiff from db.us.clamav.net
WARNING: getfile: daily-12529.cdiff not found on remote server (IP: 64.142.100.50)
WARNING: getpatch: Can't download daily-12529.cdiff from db.us.clamav.net
WARNING: getfile: daily-12529.cdiff not found on remote server (IP: 64.142.100.50)
WARNING: getpatch: Can't download daily-12529.cdiff from db.us.clamav.net
WARNING: Incremental update failed, trying to download daily.cvd
Trying host db.us.clamav.net (65.19.179.67)...
nonblock_recv: recv timing out (30 secs)
WARNING: getfile: Error while reading database from db.us.clamav.net (IP: 65.19.179.67)
WARNING: Can't download daily.cvd from db.us.clamav.net
Trying again in 5 secs...
so i tried to do it manually, is it true?

I'm already tring and searching about this issue , but still i can't find any help posts about it