If you haven’t used Sparrow yet, it’s a very polished e-mail application. The lite version is free and supports one account. Full version runs $9.99 with all options available. As of right now, the lite version is currently one step behind the full version due to Apple’s approval process.
*Inbox, Unread, and Priority Inbox filters to make your inbox feel more tidy.
*Custom signatures for every account and every alias linked to an account.
*Minimal Mode: Hide message preview in the message list and see more messages at once.
*Custom IMAP providers such as Rackspace, Fastmail, Zimbra, Dreamhost, GMX
Sparrow estimates the new version (1.1) will be available by the end of March. In the meantime, give it a try. Keeping things simple in typical Mac fashion!