Had a client that wasn’t receiving certain emails from important clients. I allowed the email address in Exchange, but the emails still didn’t go through and the sender never got a bounce back. I tested on my end and got a message that the attachment was too large.

I jumped into exchange and increased the allowable size. This article showed me how.

http://zahirshahblog.com/2010/05/25/25-may-2010-1716/