How to disable outlook to open smime mails

Hi all,
I wrote mapi extension for opening smime mails. I'm changing mail
class to ipm.note.smime to ipm.note.smime.mytype on mapi OnRead()
method.
When the user double clicks the smime mail sometimes OnRead() method
not called and outlook security system activated and ask for smart
password? But sometimes outlook fires OnRead() event i catch this
event and i change mail class and open with my addin.

I don't want to outlook security system to activated. I always want to
open smime mails with my addin.

Is there any way to disable outlook security system for this case.

I'm using office 2003 now.

Thanks in advance

Ramazan