Requires iOS 5 or higher

Features:
»Multiple Signatures (even HTML capable) for each Mail Account
»HTML Usage for Mail Composing
»Rules for incoming emails: Mark read / flagged, notification, move to mailbox, delete
»Custom notifications (Vibrate x-times, Show / Hide Popup, Soundfile or iTunes Ringtone, Speech)
»Custom volume for mail notifications
»Option: Sound / Speech notification always or only when headphones are connected
»Announce emails using Addressbook names
»Use volume buttons to dismiss notifications
»Mail Highlighting in inbox (using different colors)
»Inbox filter (Show unread / flagged / all with a single tap)
»Quick actions (Mark read / unread, flagged / unflagged, delete) using swipe
»Select / Deselect all mails in inbox

Configure options from Settings app

Screenshoots

Change Log

v 1.2-3
»Removed: Language support for Japanese due to possible copyright infringement
»Added: Option to enable Notification Summary
»Added: New Rule Action: Mail Highlighting for individual messages (very cool!)
»Added: New Rule Action: Ignore following rules
»Added: New Rule Condition: Mail is replied to
»Added: New Rule Condition: Mail has been forwarded
»Added: Language support for Spanish
»Added: Language support for Japanese
»Added: Indicator whether a rule is enabled or not (in Rules Overview)
»Fixed: Some AppStore apps crashing on startup
»Fixed: Crash when a mail account is deleted
»Changed: "Get Started" has been updated
»Changed: Sounds are now ordered alphabetically for selection

[NOTE] To activate this go to Settings app > Mail Enhancer Pro, tap on "About" and then on "License". You must be connected via Wifi or 3G while doing this, for the license to be downloaded.

Friends