Se avete installato MailScanner in Centos ed installato clamav tramite rpm potreste avere il seguente errore:

May  1 09:12:40 spam01 update.virus.scanners: Found clamav installed
May  1 09:12:40 spam01 update.virus.scanners: Running autoupdate for clamav
May  1 09:12:40 spam01 ClamAV-autoupdate[3901]: ClamAV updater /usr/local/bin/freshclam cannot be run
May  1 09:12:41 spam01 update.virus.scanners: Found generic installed

per risolvere il problema occorre aprire il file /etc/MailScanner/virus.scanners.conf
e cambiare la riga

clamav /usr/lib/MailScanner/clamav-wrapper /usr/local

con

clamav /usr/lib/MailScanner/clamav-wrapper /usr

naturalmente riavviate MailScanner