message rejected :5.2.3

Hello

I have Exchange 2010  and  have issue with message size  .

I cannot receive more than 6 MB

I f anybody send me message more than 6 MB  he received the below message from my Exchange server

This only shown if I receive from External domain not internal users .

#< #5.2.3 smtp;550 5.2.3 RESOLVER.RST.SendSizeLimit.Org; message too large for this organization> #SMTP#

please need help

MCP MCSA MCSE MCT MCTS CCNA