We ran MobileMe through our baseline CSS test, and found that there were improvements in some areas (see our Email Standards Project test result) but in other places some CSS support was actually degraded compared to .Mac rendering.
It is still a very solid client, but of course it is never nice to see the level of support going in reverse. MobileMe lost point in CSS selectors, and we saw odd results with link colours and heading styles.
CSS defined in the head is partially ignored (for example in lower level headings) but if you drop the styles inline, everything seems to render much more reliably, much like Gmail. Nonetheless, MobileMe dropped a few points in our test.
We’re already planning the next version of the CSS test, which will broaden its scope to better cover both inline styles and styles in the head, giving you as much information as possible to build emails which will render more consistently.
If you haven’t already checked them out, take a look at our free email templates which are built using all the information gathered during the CSS test.