Se si utilizza procmail come local delivery agent, è sufficiente aggiungere questa regola in $HOME/.procmailrc per abilitare il filtro antivirus con il programma sanitizer:

PATH=/usr/local/bin:/usr/bin:/bin
SHELL=/bin/bash
MAILDIR=$HOME/Maildir/
ORGMAIL=$MAILDIR
DEFAULT=$MAILDIR
#LOGFILE=$HOME/procmail.log
#VERBOSE=yes
#-------------------------------------------------------------------------
# Filter the mail with ClamAV
#-------------------------------------------------------------------------
:0 fw
| /usr/bin/sanitizer /etc/sanitizer.cfg

Il programma sanitizer si configura tramite /etc/sanitizer.cfg:

#-------------------------------------------------------------------------
# Active features.
#-------------------------------------------------------------------------
feat_verbose      = 0    # Warn user about unscanned parts, etc.
feat_log_inline   = 0    # Inline logs: 0 = Off, 1 =  Maybe, 2 = Force
feat_log_stderr   = 0    # Print log to standard error.
feat_log_xml      = 0    # Don't use XML format for logs.
feat_log_trace    = 0    # Omit trace info from logs.
feat_log_after    = 0    # Don't add any scratch space to part headers.
feat_files        = 1    # Enable filename-based policy decisions.
feat_mime_files   = 1    # Always check the mime-type's default name too.
feat_force_name   = 0    # Force all parts (except text/html parts) to
                         # have file names.
feat_boundaries   = 0    # Replace all boundary strings with our own
                         # NOTE:  Always breaks PGP/MIME messages!
feat_lengths      = 1    # Protect against buffer overflows and null
                         # values.
feat_scripts      = 1    # Defang incoming shell scripts.
feat_html         = 0    # Defang active HTML content.
feat_webbugs      = 0    # Web-bugs are allowed.
feat_trust_pgp    = 0    # Don't scan PGP signed message parts.
feat_uuencoded    = 1    # Sanitize inline uuencoded files.
feat_forwards     = 1    # Sanitize forwarded messages.
feat_testing      = 0    # This isn't a test-case configuration.
feat_fixmime      = 1    # Fix invalid MIME, if possible.
feat_paranoid     = 0    # Don't be excessively paranoid about MIME headers etc.

#-------------------------------------------------------------------------
# Create saved files using this template. The directory must exist and
# be writable by the user running the sanitizer.
#    $d - Day of month (01-31)
#    $m - Month number (01-12)
#    $y - Two digit year (00-99)
#    $Y - Four digit year
#    $H - Hour (00-23)
#    $M - Minute (00-59)
#    $S - Second (00-59)
#
#    $P - This process's PID, in hex.
#    $T - The current Unix time, in hex.
#    $T - The current Unix time, in hex.
#    $F - A safe version of the original file name.
#    $  - A random character, from [A-Z0-9].
#-------------------------------------------------------------------------
file_name_tpl = /home/quarantine/$Y$m$d-$T-$F.$$

#-------------------------------------------------------------------------
# Message used to replace attachments saved and removed.
#-------------------------------------------------------------------------
msg_file_save  = *****ANTIVIRUS*****\n
msg_file_save += ATTENZIONE:\n
msg_file_save += Questa mail conteneva in allegato il file "%FILENAME"\n
msg_file_save += che e' risultato infetto da virus o potenzialmente dannoso.\n
msg_file_save += Il file e' stato rimosso al fine di evitarne la diffusione involontaria.\n
msg_file_save += %SAVEDNAME\n
msg_file_save += *******************\n

#-------------------------------------------------------------------------
# We have 2 policies, in addition to the file_default_policy.
#-------------------------------------------------------------------------
file_list_rules = 2

#-------------------------------------------------------------------------
# 1) Scan some attachments for virus with Clam AntiVirus.
#-------------------------------------------------------------------------
# This policy apply to attachments whose file name did not match any
# previous policy and matches this regular expression.
# The policy action can be:
#
#   accept   Don't alter the attachment at all.
#   defang   Alter the attachment's file name.
#   mangle   Change completely the attachment's file name.
#   save     Remove the attachment from the message, replace it with a
#            text message and save the attachment into a local file.
#   drop     The attachment will be deleted and replaced with message.
#   unknown  Indeterminate result, check the next policy.
#
#-------------------------------------------------------------------------
# Archives, executables, scripts, etc. This is a perl regular
# expression, see "man perlre" for info. The (?i) prefix makes
# the regexp case insensitive.
file_list_1  = (?i)\.(
file_list_1 += 7z|bat|com|chm|cmd|cpl|exe|pif|scr|sys
file_list_1 += |dat|doc|m?db|ppt|pps|ppsx|rtf|xls|xlsm|xlsx|wp.?
file_list_1 += |class|pl|vb[es]|[sp]?html?|php\d?
file_list_1 += |z(ip|oo)|ar[cj]|lha|[tr]ar|rpm|deb|slp|tgz|g?z|bz\d?
file_list_1 += )$

# Virus scanner command line. The three exit codes represent the
# following scan conditions: clean, disinfected, infected.
file_list_1_scanner = 0:1:1:/usr/bin/clamdscan --fdpass --quiet %FILENAME

# What policy to apply for each exit code, plus a catch-all default.
file_list_1_policy  = unknown:save:save:unknown


#-------------------------------------------------------------------------
# 2) White list, this extensions (or Content-Type) will be accepted.
#-------------------------------------------------------------------------
file_list_2  = (?i)\.(
file_list_2 += 7z|ai|ang|an6|asc|bmp|bz2|cl|csv|dat|doc|docx|dwg|dxf|fh|gif|gz|html?|ics|indd
file_list_2 += |jc3|jc4|jc5|jpe?g|m?db|mov|p7m|od[btsgfp]|ot[btspgf]|pcx|pdf|png|pps|ppsx|ppt|pptx
file_list_2 += |psd|pub|rtf|snp|sxc|tiff?|tgz|txt|vcf|wav|wp.?|xls|xlsm|xlsx|xml|zip
file_list_2 += )$
file_list_2_scanner = 0;
file_list_2_policy = accept;


#-------------------------------------------------------------------------
# Default policy: accept, but mangle file name.
#-------------------------------------------------------------------------
file_default_policy = defang

#-------------------------------------------------------------------------
# String used to mangle file names.
#-------------------------------------------------------------------------
msg_defanged = ANTIVIRUS

Questi sono gli exit code del prorgamma clamdscan:

Quindi se il demone non risponde si ottiene un codice di uscita 2, quindi non si applicano le tre possibili condizioni (clean, disinfected, infected), verrà applicata la policy catch-all, che nell'esempio sopra è save (rimozione del file e salvataggio in quarantena).

: Forse questa non è la condizione ottimale, altrimenti una interruzione dell'antivirus porta alla perdita di tutti gli allegati.