If Microsoft Office Sharepoint Server is installed on a server that doesn’t have a local SMTP server or you could not install SMTP service becuase Exchange 2007 runs on the same server, you could use the remote SMTP server as follows:
First find the account that Windows SharePoint Services Timer runs under.
Then login to the remote SMTP server (a local server that’s part of the same domain as your MOSS server)
I assume you have already installed SMTP service on the remote computer. Browse to the default SMTP mail directory (usually C:\Inetpub\mailroot) and setup a share for the mailroot folder called MossMailRoot
Add the service account (uk\sharepoint) for the mailroot folder with full permissions.
Now open Central Administration à Operations page on your MOSS server
Open Incoming e-mail settings and set E-mail Server Display address as sharepoint.local and the E-mail drop folder as \\<servername>\<sharename>\Drop
You need to update your DNS server records to point sharepoint.local to the remote SMTP server
On the Remote server, Open IIS console and drill down to Default SMTP Virtual Server. Add new Alias domain for sharepoint.local
The server setup is complete. Now browse to your Intranet page and setup Incoming E-Mail Settings for one of the libraries.
Now When the users send an email from their Outlook client to email@example.com the email will be received by your Exchange. Assuming you have Exchange 2007, you need to configure a Send Connector so that Exchange knows where to forward that email.
The Send Connector will have the following configuration
Once this send connector is configured, Exchange 2007 will forward all emails with sharepoint.local domain to the remote SMTP server. The email will be stored in the Drop folder.
The Windows SharePoint Services Timer service monitors this folder at regular intervals as the network path is given in its configuration. If it finds any emails, it will check for the recipient email address and routes the email to appropriate Sharepoint library. After that it deletes the email message from the Drop folder. That’s why you need to give modify permissions for the service account on the mailroot folder.