SharePoint 2007 allows for emails to be accepted into discussions, document libraries and lists. To enable this functionality, a few steps will need to be followed. One thing to note: integrating SharePoint with Exchange is NOT needed for this functionality, but if you do choose Exchange, you will get some added benefits.
You will need to install the SMTP Server Service on the SharePoint server. This is done via add/remove programs, and within the IIS component listing.
-Enable Incoming Email
Now, enable Incoming Email from the Central Administration website. It is found by following: Central Administration > Operations > Incoming Email Settings
You will finally need to configure an SMTP connector within your email server so it knows where to send emails you designate for SharePoint.