This caught my eye via google alerts, emphasis is mine.

In a perfect world, all email clients would render our designs the way we intended it to be. Seeing as how browser compatibility for the web is still some way off, email client standardization would be eons away from reaching display nirvana.

Together with Outlook 2007, Lotus Notes is a very difficult email client to comply your designs with.

I left a comment explaining how Lotus Notes 8 is somewhat improved in this area.

Source: Online Marketing Business Blog: HTML Email and Lotus Notes