My client is using Outlook.com. On her W7 PC she uses Outlook 2010 with the Hotmail Connector. Every day or two she finds herself again unable to send or receive email. I remote in, open OST file in SCANPST and it has errors. After several passes -- 2 with no errors -- I open Outlook and mail is flowing again. Wait a day, same problem all over again.

Chkdsk finds no problems with the HDD. HD Sentinel reports no problem with HDD, either.

Would her having a number of folders in the Inbox cause problems when syncing with Outlook.com? She has a number of folders in the root of the account, too.  Can Outlook.com and Hotmail Connector tolerate folders Outlook's Inbox?

The OST file is about 6GB with 29K messages.

I exported all mail from 2012 and older to a PST file, then deleted them from the OST file. I moved the subfolders from the Inbox to the root of the account.

I checked the OST file using SCANPST and again there are errors. Fixed them. I then opened Outlook and started looking for a way to compact the OST file. Looked in all the usual places for compacting PST and OST files but found no such option. My suspicion is that it's not possible with Hotmail Connector and/or Outlook.com. Is this correct?

So, I left Outlook running overnight in hopes that the many deletions and folders moves will be sent to Outlook.com. I'm also hoping that the OST file will shrink of its own accord because I read somewhere that that's supposed to happen.

If none of my suppositions about the cause of OST corruption are valid, any suggestions?