outlook - HTML Emails: fallback for mso conditional? -

if you're me, eye twitching end of reading this. don't blame you.

our client has requested develop responsive html email template, 2 specifications:

1. using few images possible
2. using many "fancy css-enabled features" possible. mostly, means rounded corners on boxes.

this question executing rounded corners. gmail , apple support css rounded corners, , outlook requires vector graphics. remaining platforms, they're ok using square edges.

here's how we're detecting , executing outlook:

<!--[if mso]><v:shape>...</v:shape><![endif]--> 

works charm, outlook 2000. problem is, can't figure out how create fallback. intuition says this:

<!--[if !mso]>...<![endif]--> 

but gets ignored outright comment other email clients, , corners missing boxes altogether. ask you, fine members of community: possible deploy markup platforms except mso? perhaps there's more clever way accomplish haven't considered? or email html still stone-age attempt this?

found solution after brain-wracking. instead of this:

<!--[if mso]><v:shape>...</v:shape><![endif]--> <!--[if !mso]>[fallback goes here]<![endif]--> 

this works well:

<!--[if mso]>     <v:shape>...</v:shape>     <div style="width:0px; height:0px; overflow:hidden; display:none; visibility:hidden; mso-hide:all;"> <![endif]-->      [fallback goes here]  <!--[if mso]></div><![endif]--> 

all wrap fallback in invisible div in mso, , deploys vector solution instead.

hope helps in future!