When setting up Outlook 2010 to use IMAP to connect to Zimbra without using any encrypted connection, we got this error:
Log onto incoming mail server (IMAP): General authentication failed. None of the authentication methods supported by your IMAP server (if any) are supported on this computer.
When the same IMAP setup with SSL encryption connection is used, we receive a security warning that the target principal name is incorrect. When we proceed, we got this error:
Send test e-mail message: Your server does not support the connection encryption type you have specified. Try changing the encryption method. Contact your mail server administrator or Internet service provider (ISP) for additional assistance.