I keep getting the following error after running updates on the SBS 2008 and rebooting. No configuration changes have been made to the configurations and all have been working well. An error occurred while delivering mail to 'username@domainnamecom' on the SMTP server 'localhost'. The error code was 0x800ccc6c. Verify that the mailbox exists and that the Exchange receive connectors are configured properly.

Are you using the built-in POP Connector? SBS is a different beast. You may want to ask this in the SBS Forums: http://social.technet.microsoft.com/Forums/en-US/smallbusinessserver/threads