Without powerful spam filters nothing goes nowadays. This is no new insight for most of us, since the amount of unsolicited commercial e-mail gets more and more each day. But filtering communication always has unwanted side effects. Peter Eisentraut, developer, IT consultant and author of a book regarding spam and virus fighting with Open Source tools, will talk about consequences for the overall stability, performance and usability of the email system in general. He has been involved in some large installations for German companies and government agencies, so he made some very interessting experiences in his investigations.

Some filter systems use dirty tricks with email protocols to get along the problems, some create the plaque of bounce messages and other silently discard messages without any notification, so there is no guarantee that messages arrive their destination. Large ISPs are regularly listed on DNS block lists, and many users are indiscriminate in their application of these lists, creating more communication barriers. Sender identification techniques such as SPF do nothing to fight spam but instead discriminate users of certain ISPs and lock in users to their email service providers.

Beside these technical issues spam and virus filtering can imply privacy and legal problems since the massive gathering of email traffic can be used to harvest information about the users. Many providers and administrators are not aware, that much of their filtering activities are likely to toe the line to illegality.

This lecture will take a critical look at these issues, looking at examples, experiences and current developments in the fight against email abuse, with the goal of raising awareness among users and administrators.