mxallowd - Online in the Cloud

PROGRAM:

NAME

mxallowd - dynamically whitelist your Mail eXchanger

SYNOPSIS

mxallowd [-d] [-c configfile] [-t whitelist-time] [-p pflog-interface] [-l pcap-filter]
[-F] [-s] [-q] [-p] -f fake-mailserver -r real-mailserver -n queue-num

DESCRIPTION

mxallowd is a daemon which uses libnetfilter_queue (on Linux) or pf and pflog (on BSD) to
allow (or deny) connections to a mailserver (or similar application) if the remote host
hasn't connected to a fake daemon before.

This is an improved version of the so-called nolisting (see http://www.nolisting.org/).
The assumption is that spammers are not using RFC 2821-compatible SMTP-clients and are
sending fire-and-forget spam (directly to the first or second MX-entry without retrying on
error). This direct access is blocked with mxallowd, you'll only get a connection if you
retry.

NOTE: It is highly recommended to install nscd (nameserver caching daemon) or a similar
software in order to speed-up DNS lookups. Since version 1.3, DNS lookups are done in a
thread (so they don't block the main process), however, on very-high-traffic-sites,
mxallowd may show significantly better overall performance in combination with nscd.

OPTIONS

-b, --no-rdns-whitelist
Disable whitelisting all IP-addresses that have the same RDNS as the connecting one
(necessary for google mail)

-c, --config
Specifies an alternative configuration file (instead of /etc/mxallowd.conf)

-t, --whitelist-time
Specify the amount of time (in seconds) until an IP-address will be removed from
the whitelist

-s, --stdout
Log to stdout, not to syslog

-q, --quiet
Don't log anything but errors.

-f, --fake-mailserver
Specify which IP-address the fake mailserver has (connecting to it will whitelist
you for the real mailserver)

-r, --real-mailserver
Specify which IP-address the real mailserver has

-F, --foreground
Do not fork into background, stay on console

-n, --queue-num (only available when compiled for netfilter_queue)
Specify the queue number which will be used for the netfilter_queue-link. This has
to be the same which is specified in the iptables-rule and it has to be specified,
there is no default.

-p, --pflog-interface (only available when compiled for pf)
Specify the pflog(4) interface which you configured in pf(4). The default is
pflog0. Also see the pcap-filter-option if you use an interface which does not only
get smtp-traffic.

-l, --pcap-filter (only available when compiled for pf)
Specify the filter for pcap. The default is "port 25". See tcpdump(8) for more
information on the filters.

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