IMAP Design Errors in Microsoft Outlook 2013
Microsoft Outlook 2013 creates "This computer only" folders in IMAP email accounts for storing calendar and contact data locally. This technically incorrect approach introduces backup problems and increases opportunities for data loss.
Outlook 2013 with IMAP email accounts attempts to store calendar, task and contact entries within the account. While consolidating this data into a single email account is very desirable, IMAP technology is only suitable for email. IMAP servers do not support this form of data. Unfortunately, Microsoft Outlook 2013 stores this data in local folders in an OST cache file and shows "This computer only" warnings.
Sprinkling "This computer only" warnings in a prominent user interface is a bad smell that indicates faulty engineering and product design. Users should take steps to avoid this anti-feature or risk losing their data.
Microsoft Outlook OST files are designed to locally cache account information. For IMAP email accounts, the OST caches emails and attachments. OST files that are deleted will be recreated. OST are expendable files that improve performance speed. They are not backup files and do not offer easy data recovery options.
Conversely, Microsoft Outlook PST files are database files designed to persist user information, such as calendar, tasks and contacts. PST files offer greater reliability and, when needed, recovery utilities. PST files, unlike OST files, can be backed up.
To back up calendar, contact and tasks stored in OST files, Microsoft recommends exporting this data into a PST file. In other words, to compensate for bad engineering and design choices, Microsoft recommends users perform tedious and repetitive tasks. There is a bad smell to this advice.
Users should manually create a local PST file for storing calendar, task and contact data in Outlook 2013. This is the approach taken in Outlook 2010 and previous versions. It does not attempt to mis-use IMAP technology or store important data in cache files. It provides easier PST backups and much lower risk of data loss.