On the machine where Outlook is installed, download the Outlook CalDAV Synchronizer plugin here.
Open the installer and run the CalDavSynchronizer.Setup file. Follow the prompts. When completed, launch Outlook. You may see a warning window that some add-ins have been disabled. If so, click the option to View Add-ins. Click the option to Always enable this add-in for CalDavSynchronizer. Next, click on the CalDav Synchronizer tab in the Outlook ribbon. Click on Synchronization Profiles. Click the plus (+) icon to add a new profile. Select Generic CalDAV/CardDAV and click Ok. Complete the following required fields: Name - Type in SmarterMail - Calendar or whatever friendly name you choose. Outlook folder - Ensure this is set to the correct local Outlook folder for calendars. Click on the "..." button to the right of this field and select Calendar. Click OK. DAV Url - Enter the full mail server address with a slash (/) at the end. For example: https://mail.yourdomain.com/WebDAV/. If you're uncertain of your server's Url, use the Get CalDAV URL feature within the SmarterMail Calendar interface. Username / Password - In the username field, enter the full email address of the SmarterMail account. For the password, enter the account password or select Use IMAP/POP3 account password. Synchronization Mode - Select Outlook <--> Server (Two-Way). Click Ok to save the new synchronization profile. You can synchronize within Outlook by selecting the CalDav Synchronizer tab in the Outlook ribbon and clicking on Synchronize now.

Configure the plug-in for contacts:
 
Repeat steps #6-8 above. For the profile settings, enter the following: Name - Type SmarterMail - Contacts or whatever friendly name you choose. Outlook folder - Ensure this is set to the correct local Outlook folder for contact. Click on the "..." button to the right of this field and select Contacts. Click OK. DAV Url - Enter the full mail server address with "/ab/" at the end. For example: https://mail.yourdomain.com/WebDAV/ab/. Username / Password - In the username field, enter the full email address of the SmarterMail account. For the password, manually enter the account password or select Use IMAP/POP3 account password. Synchronization Mode  - Select Outlook <--> Server (Two-Way). Click Ok. You can synchronize within Outlook by selecting the CalDav Synchronizer tab in the Outlook ribbon and clicking on Synchronize now.