For Outlook 2013 the default maximum file size is 50GB: https://support.microsoft.com/en-us/kb/982577/

0.9 and 1.5GB are pretty puny by current standards.

>Have you tried to open the .pst file with a different version of outlook? I have a .pst file that's way bigger than those and haven't had a corruption problem - but I use outlook 2013 to open it. That being said, perhaps the tool you listed here will help. If you have a backup of the .pst file it sure wouldn't hurt to try it - but maybe outlook 365 is freakin out over the size of the file - seems like it shouldn't but I guess ya never know....
>
>
>>They are not larger than 2GB. One is about 900MB, another one is 1.5GB (approximately)
>>
>>>How large is your .pst file???
>>>
>>>>Hi,
>>>>
>>>>I have tried to fix corrupted .pst files of Outlook 365 using MS too SCANPST.EXE. But next day I get the same message of corrupted files.
>>>>
>>>>I am considering buying this tool:
>>>>
>>>>http://www.sysinfotools.com/recovery/pst-recovery.html
>>>>
>>>>Anybody used it and what were the results?
>>>>
>>>>TIA