It is also necessary to enable NTLM (SPA) authentication in email clients. These settings are generally performed in user's email account configuration. The following section provides instructions on how to set for example MS Outlook extended by the Kerio Outlook Connector:
In the View or change existing e-mail accounts.menu, select
Select a Kerio (MAPI) account and click on 28.4 Editing an e-mail account).(see figure
In the account settings just opened, go to the Account tab and enable the Secure Password Authentication option (see figure 28.5 NTLM authentication settings).