Hi Phani,
You have two options here...
1. Export/archive all mailboxes to PST file from your hosted invironment and import back with exmerge to in-house Exchange 2003 environment.
XADM: Some Questions and Answers About the Exmerge Utility
2. Use some thirdparty POP3 downloader if hosted mailboxes support POP3 service, to download mails to in-house mailboxes directly.
Amit Tank | MVP - Exchange | MCITP:EMA MCSA:M | http://ExchangeShare.WordPress.com