One way to lower this type of spam is by encouraging your customers to "munge" their email addresses. Munging is an attempt to keep robot programs that troll the Internet for addresses from recognizing yours or your customer's. This can be done by adding spaces to the email address, or by inserting "NOSPAM" or other spurious text into the end of the address. However, some company naming policies may not permit munging.
It's also a good policy for your company -- and your customer's company -- to not distribute HTML email, such as newsletters. But, having said that, it's nearly impossible, since HTML-formatted email is now the standard form of communication to clients.
This was first published in September 2006