Having been involved in the anti-spam thing for a while, I can simplify the &quot;spam solutions&quot; checklist to two items:<p>1) Do you have a solution to one piece of the spam problem?<p><pre><code>  ( ) Yes - go away, you don&#x27;t solve the whole spam problem.
  ( ) No  - go away, you&#x27;re not helping to solve the spam problem
</code></pre>
2) Do you have a solution to the whole spam problem?<p><pre><code>  ( ) Yes - go away, you&#x27;re a FUSTTSP scammer
  ( ) No  - go away, you&#x27;re not helping to solve the spam problem.

</code></pre>
The <i>explicit approach</i> by the SMTP people was both of the above at the same time.  Incremental solutions were derided as &quot;the spammers will just try something else&quot;.  Major fixes to SMTP were derided as &quot;it takes a decade to deploy a new protocol&quot;.<p>Well, it&#x27;s been a decade since I was involved.  Changes to SMTP practices mean that I&#x27;ve got jump through more hoops to prove my worthiness when I send email.  But the amount of spam I&#x27;m getting hasn&#x27;t gone down.