O'Reilly logo

SpamAssassin by Alistair McDonald

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Other Techniques

In addition to the spam detection tools and methodologies already discussed, there are a few more worth mentioning. These techniques can be used in conjunction with SpamAssassin or can be implemented on their own.

Greylisting

Greylisting is a technique used at the MTA level to delay incoming email, particularly from senders that have never sent email to the domain before. When accepting email from an unknown source, the MTA issues an SMTP code 451 to the sending MTA, which tells the MTA to try again later. Spammers generally use trojanned software that rarely tries resending an email once it is rejected, while a genuine MTA would always attempt a retry. So, a lot of spam can be blocked using the greylisting technique.

Over time, ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required