Your question is Outlook Low-Level Design. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Design Outlook (low-level design of an email client)
Asked in the Technical round 2 stage. Explain the core objects, interfaces, synchronization flow, local persistence, composing and sending behavior, and how the client should handle intermittent connectivity. If you introduce ML-assisted capabilities such as spam filtering, message categorization, or search ranking, describe their integration points without changing the core email-client design.