I cannot change the message size limit in Exchange 2013.  I still get the message in OWA of 
"The following files weren't attached because adding them would cause the message to exceed the maximum size limit of 5 mb Filename.zip"

 I have followed the article http://technet.microsoft.com/en-us/library/hh529949.aspx and a couple of others which all get you to change the owa web.config file to show
maxAllowedContentLength (set to 52430000)
and
maxRequestLength (set to 51200).
I have also run
appcmd set config "Default Web Site/owa" -section:requestFiltering -requestLimits.maxAllowedContentLength:51200000

I reset IIS and it didn't work. I rebooted the server and let it run over night and checked it in the morning with the same results.  

I tested the Outlook clients and they can send attachments without issue, it is just OWA.

What am I missing?

Hi,

According to your description, I recommend you increase the maxRequestLength value to 1024000.

If you dont get the error, the issue may occur when the total message size exceeds the maxrequestlength value.

I recommend you to check the size of this message, include attachments, subject, content etc.

If the issue persists, I recommend you refer to the following article to check your Message Size Limit settings:

http://technet.microsoft.com/en-us/library/bb124345(v=exchg.150).aspx

Thanks.