Perhaps comparing Yipple with Mobile Me is a vast exaggeration. It does not come close to all the features of Mobile Me, but it somehow has an tiny Apple feel to it (without Apple’s attention to details though).
After playing around with the interface of Yipple for a while, I got a déjà vu feeling. It somehow felt very familiar. When switching to the ‘simple’ theme it all became clear to me: Yipple is nothing but a branded version of Atmail. The only thing Yipple has done is to slap a (buggy) theme on top of Atmail and called it Yipple. What makes it even more funny is that, at least in my opinion, the default theme in Atmail (named ‘simple’ in Yipple) looks much better than Yipple’s default theme (named ‘advanced’). On top of that, Atmail’s theme works just fine in both Safari and Firefox, which is something Yipple’s theme does not. In addition, Yipple did not expand their theme to the entire service. For instance, if you switch to Calendar, it uses the default Atmail template.