Here are some good pragmatic suggestions for our "constant battle".
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Anyone with an inbox nowadays knows that email spam is a real and serious problem. Luckily there are a number of techniques you can employ to contain this phenomenon and decrease the amount of junk mail you receive.
Address munging
Spammers harvest email addresses using bots that surf the Net in search of email addresses. If an email address is hidden somehow when it's published on the Web, a bot may miss it. Address munging is the process of hiding or disguising an address. For instance, you can write an address like this: name [AT] domain [DOT] com, or create an image that displays the address, or write the address in ASCII characters. For example, when you put @ in the HTML code, the browser translates it to @.
Content-based filters
Once the spammers have your email address, the fight moves to your mail server and inbox. A simple approach to reducing spam is to filter each message's content. With content filters, the body of the message is scanned in search of trigger words, such as Viagra or free money. If one or more of these keys are found, the message is marked as spam. In some implementations you don't have a "spam/not spam" identification but instead a score (the higher the score is, the higher the chance the message is spam), so one can customize the system a little.
The main disadvantage of this method is that spammers often misspell words or hide them to avoid recognition. Moreover, using a large list of trigger words can increase the number of false positive cases ...
