You receive a message stating the BizTalk MessageBox database is too large.
When running BizTalk Server in a development or test environment, data that is stored in the MessageBox database is not usually business critical data, and therefore may be deleted. To manually purge data from the MessageBox database using the bts_CleanupMsgbox stored procedure, follow the steps in this Microsoft TechNet article: http://technet.microsoft.com/en-us/library/bb727781(BTS.70).aspx
You should only perform these steps in a test environment. Manually purging the BizTalk MessageBox database in a production environment is not supported.