Understanding Outlook IMAP account data files
As people migrate from earlier versions of Outlook (‘2010 & earlier) there is some confusion on how data for Imap email accounts is stored in Outlook ‘2013/’2016 as compared to earlier Outlook versions (‘2010 and earlier)
For the sake of simplicity, the focus will be on environments where the first email account configured in the Outlook pofile is an Imap account
Outlook ‘2010 and earlier
In earlier Outlook versions, when an Imap account is configured, two PST files are created. The first PST file contains the email folders associated with the IMAP account which are sync’d with the IMAP server. Should Outlook not find this PST file when it opens, a new PST file will be created and the folders will be re-sync’d with the server.
The second PST file is set as the default data file for the profile and will contain the default contact/calendar folders for the profile. This PST file will never be automatically be deleted if the IMAP account is removed from the Outlook profile.
In the cases where another email account was configured before the IMAP account is added, the second PST file used for contact/calendar folders does not get created. Instead, the default contact/calendar folders will be maintaied in the Outlook data file that has already been configured as the default data file for the profile.
Outlook ‘2013/’2016
An important thing to point out that surprises many people is that when people configure email accounts using auto-discover (entering only the account email address/password), it will be created as an IMAP account by default when supported by the email service provider which can have a major impact in terms of using existing data from a previous Outlook installation.
With the introduction of Outlook ‘2013, data for IMAP accounts is completely stored in an associated .ost file. When the account is the first account configured in the profile, the contact/calendar folders in the IMAP folder tree will have the added words of “This Computer Only” included in the folder description. The problem with this approach is that if the IMAP account is removed from the profile, the associated ost file is also automatically deleted meaning that data in the contact/calendar folders will be lost.
When doing an in place upgrade on the same computer from Outlook ‘2010 (earlier), the data in the PST file used for email folders is not copied to the new OST file for the account. Outlook creates a new OST file and then re-syncs with the server the next time Outlook is opened.
An .ost file can only be opened by the original Outlook profile/email account that originally created it so even if the .ost file was saved separatey, a 3rd party OST2PST conversion tool would be requuired to access the data in the ost file.
In the case where the iMAP account is not the first email account being configured, no contact/calendar “This Computer Only” folders will be included in the IMAP folder tree. Instead, the default contact/calendar folders will be maintained in the data file that is already defined as the “default data file” for the profile.
Category: Migrating Outlook, Understanding Outlook
