So you setup the smtp server on one of your SharePoint servers, and then have your email service forward all emails to that smtp server.

Exchange only is useful because it integrates with AD and thus all of your SharePoint enabled groups and lists can appear in your address book.

So you setup the smtp server on one of your SharePoint servers, and then have your email service forward all emails to that smtp server.

Exchange only is useful because it integrates with AD and thus all of your SharePoint enabled groups and lists can appear in your address book.

EDIT:

Setup stmp in iis on one of your servers, the have your email relay to that server. For example, if your email that you have setup is @sharepoint.company.com, then setup your email relay so that all email sent to @sharepoint.company.com is relayed to the smtp service in IIS on your sharepoint server.