When Exchange Server 2010 has been introduced to an existing Exchange 2003 organization some Outlook 2010 clients may report the following error when setting up a new mail profile.
An encrypted connection to your mail server is not available. Click Next to attempt using an unencrypted connection.
After trying an unencrypted connection Outlook fails to connect to the user's mailbox.
This will occur for Outlook 2010 users who still have mailboxes on an Exchange 2003 server, however it should only occur when a new profile is being created, not every time they launch Outlook.
You can create the profile by choosing the “Manually configure server settings” option instead.