Alias support seems like the big one for a lot of people.
it’s possible for you to now add aliases for your Gmail, iCloud, and Yahoo accounts.
Spark(Free) | iTunes App Store
Spark for iPhone Adds HTML Signatures, Aliases, and New Gestures
iPhone: Spark is one of our favorite email clients on the iPhone , but it’s still in its early stages. Today, they’re adding some new features that m
