Outlook 2010 for some people have started in safe mode only. Check to see if they have KB3114409 installed via Windows Update from 08/12/2015. I personally had 2 people in the last two days with this issue. It’s been pulled from Windows Update already.
Office Guides: Introduction to Office 365.
Office 365 Training: Administering for Small Business – Microsoft Virtual Academy.
03 | Office 365 Single Sign-On, DirSync & ADFS.
How to configure the size limit for both .pst and .ost files in Outlook.