1 Exchange 2010 SP2 RU6 (all roles) on 2008 R2
Mixed environment Windows 7 SP1/Office 2010
Mac OS 10.7/10.8 Office 2011 SP2/SP3
Since last Wednesday November 27 the Mac users are randomly experiencing the following error
"HTTP error. the server cannot fulfill the request.
mail could not be sent. the message has been moved to your drafs folder
error code: -18500"
It is not each Mac user and it doesn't seem to be related to messages with attachments or no attachments, replies or newly composed messages. The only change in the infrastructure is I renewed the Exchange Certificate the prior Friday November 22. No other patches have been applied to the server. I have read articles about modifying the web.config file value "httpRuntime maxRequestLength="30000" however my current value is 2097151 so I have not reduced it to the recommended setting.
There are many forums which discuss this but no one seems to have come up with a solution.
Thanks in advance.