Enabling SBS 2008 to allow remote users to use their email clients (Outlook, Outlook Express, etc.) or phones to pull down email from the SBS2008 server via POP3 or IMAP4 is just slightly more involved than on SBS 2003. For all the step-by-step details and screen shots, visit the Official SBS Blog site which details these steps in two parts (part 1, part 2).
However, you may find it helpful to view the big picture in 5 easy steps, and I will also highligh several GOTCHAS to watch out for!
Step 1: Enabling the appropriate Microsoft Exchange IMAP4 or POP3 services on the server (Start > Run > Services.msc) should be easy enough. GOTCHA #1: Be sure that you change the startup type to Automatic, and then be sure to actually Start the service!
Step 2: Enabling the required ports again should be easy enough. Port 110-POP3, 995=POP3/SSL, 143=IMAP4, 993=IMAP4/SSL. GOTCHA #2: Remember that you also need to forward port 587 as this is the listener port for SMTP/TLS mail (instead of port 25!).
Step3: From ESM (click Server Configuration > Client Access > POP3 and IMAP4), and modify the X509 certificate under the Authentication tab to point to the proper exterNal FQDN of your server (eg., remote.servername.com).
Step 4: While in ESM, move down to Server Configuration > Hub Transport, and add a new Receive Connector. Name the connector ‘Client’ (short and simple). GOTCHA #3: Be sure to click on the drop down box and change the intended use of the Receive connector form Custom to Client! You can default through the rest of the prompts.
Step 5: Finally we are done with the server setup. The only thing left is to configure your email client and test things out. GOTCHA #4: When setting up your mail client for POP3 or IMAP4, be sure that you specifcy that the outgoing SMTP connection is to be encrypted, and set the port to 587.