For a quick video overview of the material contained in this post
In Outlook ‘2010 and earlier, Contact/Calendar folders associated with an Imap email account were always stored in the default contact/calendar folders for the Outlook profile which was always a separate datastore (.pst file) from the one created to hold the Imap email folders. Where only a single email account was configured and that email account was an Imap account, a separate datastore (.pst file) was created to hold contact/calendar folders. If another email account was already configured, the default contact/calendar folders would be contained in the default datastore defined for the profile, the location of which would depend on what type of email account was previously configured.
For sake of simplicity and brevity, the following applies to either of the following scenarios in reference to Imap email accounts
#1 – There is only one account configured in the profile OR
#2 – The Imap account is the <first> email account configured for the profile
(the sequence in which multiple email accounts get configured in an Outlook profile has an impact on what data stores get created and where the default contact/calendar folders are located – for more information see <Understanding Outlook Migration – Part 3 – Email Account Creation>)
Starting with Outlook ‘2013, a single .ost file gets created when an Imap is configured which will also contain contact & calendar folders. These folders will have the words “This Computer Only” added to the folder description which means that all data contained in these folders is only stored locally. Typically, .ost based datastores are a mirror of the data that is stored on the server for a given email account. For Outlook.com Exchange ActiveSync and Exchange accounts this includes contact and calendar data but not the case for Imap accounts. (also see <Understanding Outlook PST and OST Data Files>)
The reason it’s important to understand the significance of “This Computer Only” folders is that if the .ost file assocated with the Imap account gets separated from the original Imap email account / Outlook profile that created it, the .ost file cannot be opened on its own which means the data will be lost. The only means of recovering the data at that point will be to purchase a 3rd party OST2PST conversion program which is generally expensive. Also, if you delete the Imap account from the Outlook profile, the .ost file will be deleted from the system.
To protect against contact / calendar data involving an Imap account, a simple appraoch would be to
1) Create a new PST file in one of two ways
From the Outlook Ribbon
or via Account Settings
2) Set this newly created PST file as the default for the profile. At this point, this PST file will contain the default contact/calendar folders for the profile regardless of how many email accounts are configured.
Once the above is completed, the Outlook Navigation Pane will appear similar to the following depending on whether or not the PST file was added to the profile first
PST file added after Imap Acct PST file added before Imap Acct
In the case where you want to be able to sync contact/calendar info across multiple devices, the simplest way to accomplish that would be to configure an Outlook.com account and set the data file associated with the Outlook.com account as the default for the profile. There is no requirement to use the Outlook.com for email.
The alternative to the above approach would be to remember to regularly export your contact/calendar info to either a PST or CSV file for backup purposes which will not guarantee that you always have the latest information backed up should a problem arise.