The “closest” email client to Apple Mail can depend on what specific aspect you value most: native macOS/iOS feel, simplicity, or core feature set.
Based on user feedback and design characteristics, here are a few top contenders:

1. Airmail

Airmail is often cited for its smart-looking design that feels ripped straight from Apple’s own design language, and it’s built specifically for the Apple ecosystem (macOS, iOS, watchOS). It maintains a clean, familiar interface while adding more advanced features like extensive third-party integrations and workflow customization
- Key Similarity: Very similar native Apple aesthetic and design.
- Availability: macOS, iOS/iPadOS.
2. Canary Mail

Canary Mail is another popular choice on Mac and iOS that offers a clean, intuitive look and feel, which users often describe as being Mac-like. It focuses heavily on security with built-in PGP encryption and also incorporates modern features like AI for composing and summarizing emails.
- Key Similarity: Familiar, polished, and intuitive user interface.
- Availability: macOS, iOS, Windows, Android.
3. Postbox

If you are looking for a desktop app with a familiar Apple Mail-like interface but enhanced functionality for power users, Postbox is often mentioned. It focuses on robust organizational tools, advanced search, and email templates.
- Key Similarity: A clean, professional interface with a structural layout similar to Apple Mail.
- Availability: macOS, Windows.
Other Strong Alternatives:
- Spark: Known for its “Smart Inbox” which automatically sorts emails (personal, notifications, newsletters). It has a great visual style, but its newer UI might feel less “Apple-native” than Airmail or Canary.
- Microsoft Outlook: A powerful, feature-rich option that is now free and works across all major platforms (Mac, Windows, iOS, Android). While it offers a comprehensive feature set and strong calendar integration, its interface is generally more geared towards enterprise/business users.

