Development of Exchange 2003 is set to end sometime next week. I haven't heard an "official" release date, but the article below claims it should coincide with the release of Office 2003 in June sometime.

Has anyone had a chance to use a beta version or play with this at all? I am curious specifically what changes have been made to make it more secure.

One thing I know Microsoft did was to involve more people and more organizations in the testing process and they brought in outside firms like @Stake to perform penetration and vulnerability testing.

Does anyone have any insights or opinions on whether Exchange 2003 will in fact improve email security at all? Are there any anti-spam features that actually work?

Here is an article about the new Exchange server from NetworkWorldFusion: Exchange ready to test secure code development in real world