Both outlook 2007 and outlook web access are very forgiving with the formatting of any urls you include in mail event email text.
To get a url to display properly in Outlook 2003, you have use quotations as per standard html and also add a space before and after your = sign.
Like so:
<a href = "http://myserver/workspace">K2 Workspace</a>
To avoid adding this url text over and over, and to avoid having to revisit this url throughout if there is a change (such as Development to Production) I suggest putting this entire text in the value of an Environment variable with a type: Miscellaneous Field. Then you can drag and drop in this value throughout your process and processes in the future.