Here's a suggestion:

- Get the DBA Toolkit at http://www.sqlservercentral.com/columnists/mcoles/sql2000dbatoolkitpart2.asp

- You can validate email addresses based on a regular expression similar to the following:

SELECT dbo.fn_regex_match ('^[A-Z0-9._%-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$', 'validemail@sqlservercentral.com', 'I+')

If you're using SQL 2005 you can use SQLCLR to create a regex function instead and CROSS APPLY to execute the function directly on the columns.

With SQL 2000 you'll need to play around with it.