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Fluffy the SMTPGuardDog - spam and virus filter for any SMTP server

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You can download the latest online help file from the project summary page. This is included in the full installation download.


About Fluffy (Overview)

You use Fluffy the SMTPGuardDog as a gateway (proxy) between the Internet and your existing SMTP server. Fluffy will check incoming mail connections in an attempt to filter out spam.



System Requirements

Fluffy is for Windows 95 or later. You must have an existing SMTP server that actually stores/delivers mail to individual mailboxes. This SMTP server can be running on the same computer as Fluffy (and thus run under Windows, eg VPOP3) or it can be running on any other computer system (and so need not be running under Windows). If you are running Windows 95 you need Internet Explorer version 4 or later (the current version is 5.5).

The program will run on slow hardware. My system is running under Windows 95 on a 233 MHz Pentium machine on a 128k/128k ADSL connection. It has handled 1500 x 30k messages over a period of 10 minutes without a fault. It rejects over 1200 spam messages coming in per day.

Frequently Asked Questions

Ask a question.


Download and unzip the latest version and then run setup.exe. Then set Fluffy to run on startup.

Now we need to configure the SMTP server You have an existing SMTP server that listens on port 25 (standard) for incoming mail connections. We need to have Fluffy listen for incoming mail and redirect genuine email to the existing SMTP server. There are a variety of ways to achieve that which makes this section appear more complicated than it really is. We'll present a simple case for running Fluffy and the VPOP3 mailserver on the same computer, and then go into detail for alternatives.

But first an important word on open relaying. An open relay is when your computer is set up to deliver email from anyone to anyone. This is often used for sending spam. It is something you want to avoid, especially if you pay for your bandwidth. Some SMTP servers will validate email based on IP address. This will not work with Fluffy because all email will appear to be coming from the computer running Fluffy (ie a local machine).

The preferred method is for SMTP Authentication provided that you do not require SMTP authentication for local (internal) email. Your email software must support SMTP authentication to use this option, and you need to turn it on in your email software. For example, in Outlook, choose email accounts and on the Servers tab choose My server requires authentication under outgoing email server. If VPOP3 is your SMTP server you change the settings under Services (formerly Local Servers), and enable Require SMTP Authentication and also Do not require SMTP authentication for internal/incoming mail.

If your mail software or SMTP server does not support SMTP authentication in this way, you should validate by the the From: address rather than by IP address. In VPOP3 settings, you do this by clicking on the the SMTP link (formerly Configure button), and selecting SMTP Anti-Relay Protection as Check From: Address. You should make sure Don't allow addresses with '%' in their address is enabled. This introduces another problem - what if a spammer fakes your From: address to try and use your SMTP server to send email? Fluffy will detect such attempts and prevent external (outside your network) connections from using an internal From: address as the sender of the email. If you are running a very sophisticated operation with validated relaying for some users, or just want to talk about your options for using Fluffy then you can email me or start a public discussion. Basically you can achieve what you want very simply, but you can probably work that out for yourself.

Ok, on to setting things up.

  1. Simple case of Fluffy and an SMTP Server (eg VPOP3) running on the same computer

    The simplest approach is to run Fluffy on port 25 (the default) and change your SMTP server to listen on a different port. For VPOP3 you change the settings under Services (formerly Local Servers), and set the SMTP server to use port 26.

  2. Fluffy and SMTP Server running on a different computer

    In this case you could run both Fluffy and your SMTP server on port 25. The trick is to set this up so that incoming (Internet) traffic talks to Fluffy rather than your SMTP server. It doesn't matter which system your local mail clients talk to.

    To direct connections to Fluffy you'd do so as you did for your SMTP server. For example, if you are using a NAT you'd forward port 25 connections to the IP address of the computer running Fluffy. Or if your mail server is listed in a DNS record you could change the MX (or A if you don't use MX) record for your domain to point to the IP address of the computer running Fluffy. Or you could swap the IP addresses of the computers running Fluffy and your SMTP server. Again, this may sound complicated, but that's because you have a choice of options, some of which you may never have heard of. Just ignore the ones you don't know anything about. If you need more help with this, you can email me or start a public discussion.

  3. Not running Fluffy on port 25

    You can run Fluffy on any port (eg 26) which means your SMTP server could continue to run on port 25 (on the same computer or a different one). Internet mail connections expect to talk to port 25 so in this case you'd need to use NAT or port forwarding to direct incoming (Internet) traffic to Fluffy. If you need more help with this, you can email me or start a public discussion.

  4. Other options

    There are other combinations to make Fluffy work. If you are interested in doing this, you probably have the skills to set it up. If you need help with this, you can email me or start a public discussion.

For local mail clients you don't need to change their settings. If Fluffy is listening on port 25 then you can still connect to port 25 as a default. If you are running your Fluffy on port 26 (for example) you can choose to redirect your mail clients to use port 26.

Multiple SMTP Servers

If you run multiple SMTP servers on different IP addresses (a secondary MX record) then be aware that spammers will often send to all MX entries rather than just the first. And if a spammer is rejected by Fluffy on your first SMTP server, a spammer will try your secondary server. In summary, you need a consistent filter on each SMTP server you are running. Otherwise one SMTP server will block it, but the next will accept it. One answer is to also run Fluffy for each SMTP server you have.


When you first run Fluffy you will be taken to the Fluffy Training Centre screen. Once Fluffy is running you can access the Training Centre by double clicking on the three-headed Fluffy dog icon on the notification area (system tray), and then clicking on the Configure button.

When you first run Fluffy you will be prompted to use the default DNSBL servers, default Spam Trap address list, and default Black/White lists. If you choose to use any of these, you should then edit them for your own use.


When Fluffy is running, a three headed dog icon appears in the notification area (system tray) near the clock. Double click on the Fluffy icon to bring up a window displaying the current log file and control buttons. Click on the Configure button to train Fluffy. Click on the Shutdown button to send Fluffy to sleep. If Fluffy detects a serious issue for your attention a red icon with a white bar will appear in the notification area - the message is also recorded in the log file.

Log Files

Log files are stored in the file logyyyymmdd.tx where yyyy is the year, mm is the month number, and dd is the day of the month.


A change log tells you what has changed from previous version

Version 1.4

Version 1.3

Version 1.2

Version 1.1

Version 1.0

Version 0.9

Version 0.8

Version 0.7

Version 0.6

Version 0.5

Version 0.4

Version 0.3

Version 0.2

Version 0.1

Things to Do


Fluffy the SMTPGuardDog Copyright (C) 2003 Wayne McDougall

Help files Copyright (C) 2003 Hairydog Ltd

Fluffy comes with ABSOLUTELY NO WARRANTY; for details read GPL.txt

This is free software, and you are welcome to redistribute it under certain conditions; read GPL.txt for details.

The help file was developed by Hairydog Ltd in grateful thanks to the creators of Fluffy. At Hairydog Ltd, we specialise in software documentation and help systems, web site design, development, maintenance and hosting.

We produce help in winhelp, htmlhelp, webhelp, javahelp and other formats.

Contact us - we can help you:

You won't get the hard sell. We're more interested in doing a good job for our clients!

Hairydog Ltd
Tel +44 (0)845 124 9504

Download Fluffy

You can download the latest file releases from the project summary page

You can check out the latest source code in development using CVS

Fluffy Project hosted at Sourceforge.Net

This website and these services are kindly provided by Sourceforge.Net. You can acces all these services, and more, at the Fluffy Project Summary Page. If you want to post a message or join a mailing list, you need to login to Sourceforge.Net. If you are not an existing member you can create a new account for free.

News about Fluffy

You can read any news about Fluffy. We report on new versions and anything that may affect your use of Fluffy. You can add your own comments to news items if you login.

Feedback and Support

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You can report any bugs, ask for help or request new features in the online tracking system