How To Fight Spam Using Your Postfix Configuration

hausmasta writes, "In this guide you will learn how to tweak your virtual Postfix setup to better combat spam by stopping the mail before it hits SpamAssasin, using RBL (Realtime Blacklists) and RHBL (slightly different), greylistings, and Helo Checks." A clear, step-by-step guide to a complex subject.

Comments

Re:RBLs and not getting your mail

[grasshoppa]

If you're running the mail servers for a business, how prudent is it to run a spam filter in the first place? While using something that relies on checking the content of the mail may be useful in getting rid of the most egregious spam, you don't want to block all items identified as spam. You can't run the risk of blocking your customers.

New to the business? You don't block anything in this situation; You mark it with a header ( that's part of the email message that you would likely never see. Most mailers won't display them unless you ask it specifically to do so ), and leave the blocking/filtering up to the end user.

For my uses, I have spamassassin running with a couple RBLs ( both in house and external ). I don't delete any mail; It is instead redirected to a specific folder when it's identified as spam. Over the past 6 months spam has made it into my inbox twice, and i've had no false positives.

If you know what you are doing, this is the ideal solution.

RBLs are notorious (especially SpamAssassin) for blacklisting entire domains when only a small subset of those users are actually sending spam.

Uh, no they aren't. Spamassassin isn't an RBL.

There are a few RBLs that are notorious for their blocking behavior, and as such, few use them.

If you're running your own mail server at home, then a whitelist would probably be more useful than a blacklist since you already know who you want to contact you.

I'd agree with this; Automated whitelists are the way to go.

But you gotta hand it to the Unix folks for making the task of setting up a spam filter this difficult.

It's only difficult when you don't understand the process.


I am curious how difficult it would be to set up a spam filter on an Exchange server.

Curiously enough, most of the time I hear people recommending placing a spamassassin enabled email server in front of an exchange server if you want decent spam protection.

Overall, I'd give your post a 9/10 on the troll scale. It wasn't bad, had factual data twisted in such a way as to be completely false. I even bit, not to argue with you but to make sure innocents don't read your post and get confused.

sendmail tweaks

[ltjohhed]

A far more effective and less faulty way to filter out some spam can be done by using the new features added in sendmail 8.13.

FEATURE(`great_pause',5000)
That one is given in your .mc file.

Wait's 5000ms to say HELO (EHLO) and all MTA's starting to send data (spambots not being all that RFC-aware) before that is discarded.

I've measured that it atleast cuts 15-20% of the total amount of spam.