We're in the third quarter of 2014, and for generations now toddlers have been learning the mantra "Don't use tables for layout". Alongside that, there's less and less certainty that people viewing the e-mail I send will be using a desktop monitor – so 'fixed width' is also less than ideal. This is only a mail-merge question in the sense that it's mail-merge that prompts Word to switch from 'good enough' print layout into 'less good' Web layout.
Reformulating the question: can I use the Office mail-merge functions to send fully-formatted e-mails that use CSS for a simple, flexible three-column layout? if so, how do I set about it?