Event series not working

[Saim Kim]

Hello everybody,

yet another problem :-(
When I try to send an event series to somebody else  I get the following 
error message:

<somebody at mydomain.com>: Command died with status 255:
    "/kolab/bin/php". Command output:
    2873,/kolab/lib/php/Net/IMAPProtocol.php,PROTOCOL 
ERROR!:UNIMPLEMMENTED! I
    don't know the parameter 'NOMODSEQ' !!!
    2973,/kolab/lib/php/Net/IMAPProtocol.php,PROTOCOL ERROR!:bogus 
response!!!!
    (COMMAND:OK) 2873,/kolab/lib/php/Net/IMAPProtocol.php,PROTOCOL
    ERROR!:UNIMPLEMMENTED! I don't know the parameter 'URLMECH' !!!
    2873,/kolab/lib/php/Net/IMAPProtocol.php,PROTOCOL 
ERROR!:UNIMPLEMMENTED! I
    don't know the parameter 'INTERNAL' !!!
    2973,/kolab/lib/php/Net/IMAPProtocol.php,PROTOCOL ERROR!:bogus 
response!!!!
    (COMMAND:OK)

How can I get this to work?

Best regards,
Saim