We had a user on Office 2011 who upgraded to El Capitan and doing a rebuild of their Outlook database fixed it. This is connected to Exchange 2013 too.
I'm curious if anyone is having issues with Office 2016 and El Capitan ? Paul Thurrott said it's unusable, but I haven't noticed any issues yet.
"Office 2016 on El Capitan is unstable and virtually impossible to use on my machine; all of the apps crash multiple times a day. To top it off, I have had the error reporting mechanism crash (above image) while trying to send my crash log after Outlook bit the dust. The crashing is so bad that I cannot trust the apps to work long enough to accomplish anything meaningful which renders my Mac useless for daily tasks."