Opera Mail Portable (Discontinued)

Opera Mail is a lightweight, customizable mail client that makes reading, labeling, and filtering messages easy.

• More efficient mail - The way you read mail just got better. Elegant tabs allow you to view multiple emails messages at once and navigate between them with ease.
• Work smarter, not harder - Threads help you smartly organize your mail. Keep up with the context of any mail thread, and quickly view previous messages in the conversation.
• Sort messages intuitively - Labels allow you to sort your messages quickly. Take control of your inbox and set simple rules to sort mail automatically.
• Keep up with your favorites - Opera Mail's built-in feed reader provides automatic notification of updates to your favorite websites.