In this time is not possible to add two or more full Kerio accounts in to outlook. Its not supported by Kerio. Exchange this officialy support from Outlook 2010SP1, but this working very strange.

So, first solution is add another account as pop3 or imap account :
Setting up a second email account in Outlook with KOFF

Second solution is add mailbox as delegated mailbox with full rights :
Using delegation in Kerio Connect client
Using delegation in Microsoft Outlook with Kerio Outlook Connector