hrmm, this issue seems to be with or without tls enabled.
I currently have ours setup with zmtlsctl both previously was redirect but for attempting to add an internet calendar I've changed this to both.
I have tried with webcal or http links and even inserting the username and password similar to how thunderbird has it setup and still cannot add the calendar to Outlook 2007.
I've tried -
and all the above combinations with http and https without any luck.
I know I could simply use the connector but I already have all our staff setup without it and would like to continue without it (older people simply don't like change).
Any help greatly appreciated!