1) User level requirement(s):
- Send/receive emails to/from any domain securely and efficiently.
- Store emails securely for future reference.

2) Functional requirement(s):
- Develop user-friendly email interface for composing and sending emails.
- Implement efficient email retrieval system.
- Create secure and reliable email storage.

3) Non-functional requirement(s):
- Performance: Ensure efficient email handling.
- Security: Implement strong encryption and authentication.
- Reliability: Ensure smooth email delivery and retrieval.
- Scalability: Design system to handle growing user base.
- Compatibility: Ensure compatibility with various email protocols and domains.