I have just seen an offer where it costs 10 euro per month and the features are:
1 GB RAM and 25 GB Hard disk.
I don’t know how much space setting Windows 2008 R2 + Exchange 2010 could take up. Would it be enough those 25 GB ?. It is only for learning purposes, so it is not going to be many mailboxes, hence, not much space in that regard.