From what I've seen, there definitely is email capability in RS for SQL 2000, and various sources say that there are absolutely no differences between
using RS 2005 on top of SQL 2000 versus using RS 2005 on top of SQL 2005, except perhaps the licensing (which is another issue). That is you still need a SQL Server 2005
license for whatever box is running RS 2005.
Anyways, SQL Server RS 2000 + SP1 = SQL RS 2005. There are some articles that discuss upgrading Reporting Services from SQL Server 2000 Reporting Services to the version that ships in SQL Server 2005.
Below are some links that might be interest. Hope this helps! Let me know.
Also, an article that just published today on SQLServerCentral.com --> http://www.sqlservercentral.com/col...ptions.asp