Understanding 3rd party backup programs and IMAP ost files
Many people use 3rd party backup programs to safeguard their data only to be surprised that not everything gets included when the need arises.
In terms of Outlook files, many programs do not include .ost files when backing up data. The reasoning behind this is that .ost files are mirrors of what is contained on the server for the email account and as such will get automtaically recreated and resync’d with the server which is true and valid if this involves an Outlook.com/Exchange account which also sync’s contact/calendar data.
However, starting with Outlook ‘2013/’2016, an IMAP accounts also uses an IMAP account with contact/calendar folders having the added words “This Computer Only” which means any data in those folders will be lost when Outlook re-creates the .ost file. So unless these folders are manually backed up (exported) to a PST file, that data will be lost.
Related articles on how to circumvent this problem
How to Protect Outlook ‘2013/’2016 Imap Contact/Calendar Data
How to sync POP3-IMAP contact/calendar data
Category: Outlook - How To
