Problem: OST still gets created and continues to grow after switching Outlook to Online Mode
If above mentioned error arises then it appears due to a GPO setting was enabling folders for offline use hence if we are trying to uncheck the cached Exchange Mode it will not remove the Offline Use Settings on the folders and Offline .ost file gets created.
Following fixtures can be applied to fix this type of error.
Close Microsoft Outlook
Open Control Panel > Mail >Choose profile you are working with > choose properties > More settings > Advanced Tab
Make selection of Offline Folder File Settings
Choose Disable Offline Use after that opt for “Yes”
Delete the ost file and reopen Outlook, you will observe that the send/receive folders are not available OST does not get recreated
Note, this was the solution for this issue. You can also learn about how to fix Outlook OST file is in use and cannot be accessed error in second blog post.