I\'ve never seen an amazing order confirmation / invoice email. Even the best html5 websites send terrible order confirmation emails (sometimes in plain text). I believe thi
You can use liquid layout so set all width and to be in percentage. I would also look into grid layouts or column layouts.
So far most big sites like eBay Google and so on still use tables to send out their emails. Tables are are still useful and used widely but with the new css3 like flex, column-count, grids .. tables will probably deprecate in the future.
Again the new CSS3 features are still in testing so not compatible on all browsers.
http://www.w3schools.com/css/css3_multiple_columns.asp
http://www.w3schools.com/cssref/css3_pr_box-flex.asp