imaps TLS problem

[RJ45]

Hello I installed postfix-2.0.3 + cyrus-sasl-2.1.11 + cyrus-imapd-2.1.11
everything works fine!
I use cyrus with service imaps.
the problem is with outlook clients, Netscape works fine with it.
When a Outlook client is accessing to imaps service, cyrus closes
connection and here is hte error:


Feb  5 15:37:50 venus master[364]: [ID 392559 local6.debug] about to exec
/usr/local/cyrus/bin/imapd
Feb  5 15:37:50 venus imaps[364]: [ID 518349 local6.debug] executed
Feb  5 15:37:50 venus imapd[364]: [ID 921384 local6.debug] accepted
connection
Feb  5 15:37:50 venus imapd[364]: [ID 798856 local6.notice] imaps TLS
negotiation failed: xiexie.something.it[192.84.x.y]
Feb  5 15:37:50 venus imapd[364]: [ID 637875 local6.error] Fatal
error: tls_start_servertls() failed
Feb  5 15:37:50 venus master[330]: [ID 310780 local6.debug] process 364
exited, status 75

I have no clue about this I have no details on this error.
anyone could give me a hint?
I cannot force user to use Netscape Messenger instead of Outlook.
thank you

Rick