From Zimbra :: Wiki

After installing the Zimbra Connector for Outlook (ZCO), you must create a profile that Outlook will use to log on to your Zimbra mailbox. On a fresh install, the ZCO installer will create a default profile named "Zimbra". You can use this profile or create a new one.

You must not add a "Zimbra" service to an existing profile. E.g. You must not log on to Outlook using an existing IMAP profile and select "Tools->Email Accounts->Add a new email account" and proceed to configure your Zimbra email account. If you do this, the Zimbra service will not be the default store and will cause unexpected results.