CSS properties which add visual decorations but are not supported can be replaced with image tag.

For example: border-radius is not supported in Yahoo! Mail, Outlook 2007/10/13 +, Outlook 03/Express/Mail & Android 4 (Gmail) +

To work around this we can add images with border radius in them i.e buttons with left & right side as image:

<td><img src="img-border-left.png"><td>
<td style="background: #000; color: #fff">Button Text</td>
<td><img src="img-border-right.png"><td>

Here is a list of property that should be avoided and used as image instead:

border-radius, text-shadow, box-shadow, text-fill-color & text-fill-stroke