I have seen a lot of entries and how-to's on email enabling SharePoint lists in WSS3/MOSS2007 and Exchange 2007/2003.  However, not many of them (if any) covered all the steps from start to finish.

Step 1:  Read Microsoft's entry on how to configure SharePoint, Active Directory, DNS and other settings to get most of it done here. <a href="http://technet.microsoft.com/en-us/library/cc262947.aspx">http://technet.microsoft.com/en-us/library/cc262947.aspx</a>.  It really is a fully comprehensive article on how to configure SharePoint, AD and DNS to allow creation of email enabled lists.  It does have on glaring hole though.  It doesn't specify how to configure Exchange Server to pass email on to the virtual SMTP server that is set up on the SharePoint WFE server.

Step 2:  Configure Exchange:  Configuring exchange comes with two easy steps.
<ol>
	<li>Configure accepted domains.  For your sharepoint email address specified by the Step 1.  You need to configure and accepted domain in Exchange 2007.  Go to Management Console -&gt; Organization Config -&gt; Hub Transport -&gt; Accepted Domains Tab and right click.  New Accepted Domain.  Fill out the form and specify this domain as External Relay Domain.  Once created you should be all set.</li>
	<li>Proceed to the Send Connectors Tab.  Right click to create a new send connector again with what name you specified.  The address space is going to be *.yourname.yourdomain.com.  The Network is going to be the FQDN of the SharePoint WFE server and the Source Server is going to be the list of exchange servers you have in your exchange farm.</li>
</ol>
Log off and you should be good to go.  In Exchange 2007.  You can go to Tools -&gt; Mail Queue to see the queued emails sent to the SharePoint lists.  If they get stuck in this list something is misconfigured on your Exchange server.  Otherwise they should move on to the drop folder of the virtual SMTP SharePoint server for pickup by the timer service.

Good Luck!