simta-mscan

simta-mscan is the reference implementation of a content filter for the simta MTA. Details on the content filter interface used by simta can be found here.

simta-mscan is a POSIX-compliant shell script that is designed to run under the Debian Almquist shell. The script does not actually do any filtering itself, it sources individual filters (which must also be written in POSIX-compliant shell) from /etc/mail/filters. These filters must be marked as executable and will be run in lexicographic order.

Filter example

#!/bin/dash

from_domain=${SIMTA_SMTP_MAIL_FROM##*@}
if [ "x$from_domain" = 'xexample.com' ] || [ "x${from_domain#*.}" = 'xexample.com' ]; then
    log "10_testfilter: matched domain $from_domain"
    filter_exit $MESSAGE_TEMPFAIL
fi

if check_tfile; then
    fgrep -q 'XJS*C4JDBQADN1.NSBN3*2IDNEN*GTUBE-STANDARD-ANTI-UBE-TEST-EMAIL*C.34X' $SIMTA_TFILE
    if [ $? -eq 0 ]; then
        log "10_testfilter: found GTUBE"
        filter_exit $MESSAGE_REJECT
    fi
fi