Which do you think is worse? Letting a few spams through, or not letting a few real messages through. This seems to be a problem everywhere I look these days. The accountability of email is being called into question more and more frequently. The excuse " I didnt get your email " is becoming more and more believable.
Good news for some I guess.
Welcome to the future.
The date is twenty-oh-seven. The enemy wanders the landscape raping and exploiting inboxes at will. The victims are countless as the silent war wages on with no end. As the numbers soar higher and the faltering governments of earth fail time and time again to stem the plague a new era of warrior emerges.
The MAIL DEFENDER.
These days, who isnt sick and tired of spam?
We all get it. We all hate it. Its a time waster and a general nuisance. But what can you do? Well there are all sorts of tools available to help you fight back. Pick up your guns and square off your sights on incoming junk mail.
Some tools are free. Some are not. Some are standalone. Some are subscription. There are almost as many tools available as there are pieces of spam. Something will work for your needs.
SMTP is a pretty straightforward protocol, and thats why it is so simple for spammers to mess with, but it also makes it easy for us to test if its working.
Many times you want to verify your server before bringing it live in your MX record or even just test to make sure everything is good on your sendmail side.
Simple way of doing this is using telnet from the command line:
$ telnet your.mail.server.name.com 25
Trying your.mail.server.name.com…
Connected to your.mail.server.name.com.
Escape character is ‘^]’
Most ISPs these days have blocked port 25 from sending out to the real world as a method of stopping spammers from running wild on their services.
I don't mind that normally, but I travel a whole bunch and use my own servers for email sending. By blocking port 25, i run into situations in hotels and other locations that leave me unable to send email easily.
One quick and dirty way of dealing with this is by running a simple proxy on your server with some authentication in it.
There are a number of different anti-spam proxy servers out there, basically machines, or virtual machines that run on your server, take port 25 traffic and can filter out the junk, and forward on the good stuff to your real mail server.
What surprised me over my years of consulting is how many of these devices are setup improperly to begin with, and how that isn't going to help lower that spam count in your bosses email box on a daily basis.
Back in the early infancy of the internet, before it was a capital I, the authors of RFC 821, otherwise known as SMTP didn't really plan for the explosive commercial growth this medium would one day have. They gave us only basic means of authenticating that a mail server was legit and because of that, we have our lovely chore of cleaning out our spam (or saving it into a folder!) every day and learning that there are tons of singles waiting to meet me on website_x.com.
No matter how good your spam detection method is, sometimes that elusive spam may slip by, and those are your gold.
Many spam softwares use methods similar to spam assassin, which really is an algorithm that takes certain factors and gives every email a "score" of how likely it is to be spam, or how likely it is to be a legitimate email, or Ham in their jargon.
