Update Rollup 6 for Exchange Server 2007 Service Pack 1 Released

Dvord Direwood : You can install exchange server evaluation and not apply exchange server keys. If you buy an enterprise edition of server 2008 and use Hyper-V, you can freely install up to 4 standard version of server 2008 on Hyper-V.

I think importance of testing your exchange server is a lot more important than testing licenses and servers.

Or get a Technet/MSDN license you will get some test server licenses, HWs not included.

If you have your own business you can become a Microsoft partner (https://partner.microsoft.com/US/Partner?lc=1033) and buy "Microsoft Action Pack Subscription"

https://partner.microsoft.com/US/40016455

https://partner.microsoft.com/US/40016455 -> it used to be around $150 and have all sort of products like servers exchanage and all desktops, office and CALS and so on.

I don't know the price now a days. Good luck.