MailStripper Pro 1.3.2 review

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MailStripper is an SMTP spam filter with anti-virus capability, and is Mail Transfer Agent (MTA) independent. This filter software

License: Other/Proprietary License with Free Trial
File size: 0K
Developer: Michael McConnell
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MailStripper is an SMTP spam filter with anti-virus capability, and is Mail Transfer Agent (MTA) independent.

This filter software works with SMTP-based MTAs by filtering the incoming SMTP stream. This will stop spam from reaching your mailbox.
See what MailStripper can do for you.

MailStripper makes it simple to stop spam - it is much easier to install and configure than any other SMTP spam filter. Try it now and you can have your Linux, FreeBSD or Solaris mail server protected in minutes!

Here are some key features of "MailStripper Pro":
Administrator configurable keywords list

MailStripper's main search core uses an enhanced keyword scan, entirely configurable by the site administrator. Negative biases can be used to denote non-spam keywords. Keywords may be included as a plain string or as regular expressions.

Maintained keywords list

As an alternative to maintaining your own keyword list, the config tools can download a remotely maintained keyword list (by default, the one we use at Eridani) from the website at the push of a button. You may even download a keyword list then tailor it to your own needs. This is a subscription service, with a non-subscription version that is updated monthly.

Automated updates

Synchronise your server with a central point of control. MailStripper uses cron to manage the scheduling.

Spam Bin as SMTP mailbox

The spam bin can be a local mbox-format mail file. Alternatively, a local email address permits the spam bin to be held on a different machine.

Per-user and/or per-domain spam bins

Individual spam bins per user, or per hosted domain. For example /var/spool/spam//. This facility can also work in conjunction with the Spam Bin as SMTP mailbox feature.

Subject line tagging of spam

Instead of using a spam bin, all (non-blacklisted) emails are sent on to the intended recipient, but those which would have been quarantined get a subject line tag instead. Some email clients can use this to operate a user's own local spam bin.
As of MailStripper 1.3.0 this may be configured on a per-recipient basis.

No bounces generated by MailStripper

Most spam and virus mail headers are forged. The apparent sender address is most likely not the offender. Therefore, spam and viruses are quarantined and not bounced, effectively being blackholed. (Blacklisted sites get a User Unknown error at the SMTP layer.)

Sender whitelist

The sender's email message is checked for viruses (if configured) but not scanned as potential spam. Unless found to contain a virus, the message is delivered unfiltered.

Sender blacklist

An SMTP User Unknown error code is sent to the blacklisted sender on identification of the recipient.

Source IP blacklist

An SMTP User Unknown error code is sent to the sender at the blacklisted IP/netblock, on identification of the recipient.

DNS blacklist (DNSBL) support

In addition to building up your own IP blacklist, this enables use of third party blacklists elsewhere on the Internet.

Spammer IP Honeypot

If given a list of "honeypot" email addresses (those which have no right to be receiving email, maybe inherited from a previous owner of your domain) any IP address seen to be emailing them will be automatically added to the IP blacklist. It is also possible to mark certain IP addresses as authorised relays so they won't be blacklisted even if spam comes through them - but they will be subject to the other checks.

Recipient Whitelist

Overrides any blacklists, and disables spam scanning for the named recipient. Ideal for role accounts such as abuse and postmaster.

Mail server daemon independence

MailStripper works at the SMTP level, and can be on a different machine to your MTA. It connects to your mail server over another SMTP connection.

Switchable ESMTP support

Some mail servers have issues with proprietary ESMTP extensions. ESMTP support may be disabled entirely if running ESMTP causes problems.

Intelligent anti-spam evasion countermeasures

MailStripper recognises and counteracts attempts at evading detection as spam.

Rate limiter

This will prevent your mail server from being overloaded by spam. This is a configurable option - faster servers can allow more concurrent scan processes.

Anti-virus capability (optional)

Scans all mail for virus infection, and quarantines all infected email. Frisk Software's F-Prot and NAI's McAfee uvscan are directly supported, and a new AVWRAP interface allows the use of antivirus scanners that are not directly supported by MailStripper. Our example AVWRAP script blocks Win32 executables and is supplied with MailStripper.

Does not require cutting-edge versions of libraries or MTA

MailStripper is supplied as statically linked binaries (apart from glibc on Linux), so they contain all the extra library routines they require. By working on the SMTP layer, MailStripper is totally independent of your MTA platform, let alone MTA version.

Multi-process architecture

This ensures that should a hitherto unknown malformed email message crash MailStripper, only that scanning process dies - it does not remove your system's ability to receive email.

No usage expiry (except evaluation licences)

Paid licences do not expire - there is no need to re-register every year (as is becoming common with many software packages). This does not apply to the blocklist subscription service but is not required to run MailStripper.

No mailbox limit

MailStripper will protect as many mailboxes as your mailserver can hold.

No additional licence charges for multi-processor machines.

Commercial Licences are per machine, not per CPU. Personal licences are per household.

Features an easy-to-use configuration GUI, xmstripconf

As with other X apps it can use a remote display, so you don't need to run an X desktop on your mail server.

Text-mode menu-driven config tool, mstripconf

If you're on an X-less machine or a remote session, use this to configure MailStripper instead.

Handle ESMTP "SIZE" whether or not the mail server supports it

Enforce a message size limit with this feature, rejecting anything that is too big.

Plug-in support

A very exciting new addition to the MailStripper feature set, this facility allows MailStripper to be expanded almost without limit.
This also allows for third parties to offer bolt-on services to enhance MailStripper with their own technologies. System administrators can also create their own filters based on local policies.

MailStripper supplies two plug-ins as standard - Local Blocklist and SURBL (see below).

Local Blocklist support

An often-requested feature, this has previously been a very risky change to the software core due to the changes that would be required (which is why it hasn't appeared yet).
With the plug-in facility, this can now be implemented reliably and entirely without risking the rest of the system. The local blocklist will remain untouched when the main blocklist is updated using the automatic update facility.

Spam URL Blacklist support

This is implemented as a plug-in that implements the interface described at Unlike standard DNS blacklists, this reports on the URLs contained within the body of the message.

What's New in This Release:
A potential buffer overflow in the library code has been corrected, and a bug affecting plugin response codes has been fixed.
A long-standing bug causing threads to hang without using any CPU time has also been fixed.
Recognition of a new method of junk hiding has also been added.
In the SURBL plugin, there are numerous updates, including fixing a URL parsing bug in the SURBL plugin, adding bitwise filtering to SURBL DNS responses, and amending the SURBL debug responses so they are no longer specific to and are shown as a bitmap with the corresponding bitmask.

MailStripper Pro 1.3.2 keywords