You may want to include a BASE tag in your HTML email so your recipient's browser knows how to interpret document-relative links. The BASE element allows global reference information to be set. Use of the HREF attribute provides a base address for the interpretation of all relative URL references in a document, when that document is read out of context. The TARGET attribute specifies a global frame destination name to be used for page activation changes (in links, forms and image maps). 

For example:


<BASE HREF="http://www.florentinedesign.com" TARGET="_top">