The ONLY way to not have spam is to BLOCK it.

I get a lot of spam, I mean LOTS of it. By choice. If I wanted to initiate a system wherein only those in my address book or who have verified they are a human, as opposed to machine generated spam could reach me I could, as I’m sure many of you have done.
With these systems, known as challenge / response systems, everyone who emails you gets a message asking that they reply or click on a link to verify that they are a human. Once this is done their message gets through to you.
Those who are in your address book or otherwise verified get their email message through to you.

Personally, I don’t like challenge response systems as I think it sets the barrier too high for those who are trying to email me – forcing them to justify that their email should reach you when I WANT their email.
HOWEVER, DigiPortal’s ChoiceMail makes a convincing argument, which Joanna Sorocki, Editorial Assistant, has summarized below.
There are several ways to block spam. The most reliable methods is the ?Identity-Based Challenge/Response.? This method forces the sender to identify who they are and their purpose for contacting you; without answering these questions, they cannot enter your inbox. You can also block them if there answers are unsatisfactory.
Spam is considered a violation of personal space. You should only allow people to contact you whom you know or who are offering something you are actually interested in.
There are two portions of this program. The ?Identity-Based? portion seeks to clearly identify who is sending the email. It also allows for a safe email list to be derived from address books and future emails.
The ?Challenge/Response? portion sends out ?challenges? to email senders forcing them to identify themselves. The equivalent of these challenges would be like asking someone who knocks on your door ?Who are you?? before letting them in. Challenges are considered controversial by certain people who seem to object to a sender having to identify themselves and who also claim that too many challenge messages will ?be bad for the Internet.?
Today, spam accounts for over half of all email. Email was first considered simply as another mailbox where junk mail could be easily discarded; however, email addresses have been bought, gathered and sold illegally. Now, it seems like your email address is public domain rather than a private address. To challenge a message, the receiver must be interested in the subject line and then will send a challenge message to a viable return address that must be answered with human intervention. These requirements should help eliminate spam by making it less economically feasible.
Two groups who would also be influenced in this decision besides marketers would be the press and major ISPs. Major ISPs are concerned that the challenge program would flood their internet traffic. Still, since spam is a major source of that traffic, eventually traffic would decrease. The technology press would be part of the campaign to promote the ?Identity-Based Challenge/Response System.?
?Simply put, an ?Identity-Based Challenge/Response System? world is a world without spam, period.?