Mail Enhancer adds a great deal of extra functionality to your jailbroken iPhone, including the ability to set custom signatures for different accounts, tailored notifications, advanced mail sorting options, and account highlighting. If the stock version of iOS simply doesn't meet your needs, and you're looking for more and better functionality, give Mail Enhancer a try.
iOS lacks the ability to have more than one e-mail signature. (That's why we all see "Sent from my iPhone" so often.) If you have a different account for home and office, for example, you're forced to include the contact information for both and delete the inappropriate one each time, or neither, and enter it in manually on a case by case basis. If you remember. Mail Enhancer allows you to add as many mail signatures as you'd like. Not only can you set them per account, but you can take it one step further and also have separate signatures for composing, replying, and forwarding.
Mail Enhancer also has advanced notification controls built-in. You can set mail accounts as high priority and low priority and adjust notifications accordingly. For example, you can set up high priority email to use popup notifications but have them turned off for low priority email.
If you're the type of person that likes to view all of your e-mails in one thread, Mail Enhancer makes it easy to set highlight colors for each account. That way, even when you're viewing the unified inbox, you can still easily identify which account each email was sent to, without having to tap into each one individually. You can also add a bar to the top of your Mail app that allows you to easily toggle between all your messages and just unread messages.
Mail Enhancer is already available in Cydia, the jailbreak app store.
$4.99 - Cydia Search Link
Additional jailbreak resources: