The below links are clear use any of them
http://exchangepedia.com/blog/2007/09/exchange-server-2007-setting-message_10.html
http://exchange-genie.blogspot.com/2007/11/how-to-set-message-size-limits-in.html
http://technet.microsoft.com/en-us/library/bb310771(printer).aspx
http://www.msexchange.org/articles-tutorials/exchange-server-2007/management-administration/exchange-2007-message-size-limits.html
Discuss This Question: 2  Replies
Set-Transportconfig –maxsendsize
Set-Transportconfig –maxreceivesize