A question I got today via email was around sending emails using OWA 2010. The user can send an email with a file of 42mb (attachment) using Outlook (I know, it is big). It is a media company and I guess they are sending large pdf files via email. But it fails while using OWA 2010.
The issue here is that OWA 2010 works with the settings in an xml file, named web.config. It is in the ClientAccessOWA folder.
The web.config file has a maximum attachment size of 35000KB hard coded and as the user was trying to attach a file more than the hard coded limit, it failed.
To fix the issue, open the web.config file using notepad and change the value of maxRequestLength from 35000 to the desired value (note that the value is in KB). The recommended value will be the maximum size that is allowed in your organization. The change has to be made on all CAS servers, if you have more than one.