when you configure your ms outlook with IMAP email server then it will save you all data in offline ost file as there are various reasons for the corruption of ost file but to save yourself from this errors you have to back up your data timely to ensure that your data will be safe but if you are facing corruption this time then you can use import/export option to fix those errors but it can't save files every time and it is alow so you can try universal method by using an ost to pst converter tool that can recover you IMAP ost file and convert it to PST.