It can be buggy, occasionally has issues playing nice with Gmail, and lacks some more advanced features that are present (and have been present for years) in other third-party email clients. While Mail.app provides a free, full-featured email client on every Mac and has even pioneered some innovative features over the years (like VIP and Handoff), it’s definitely not for everyone. The Mac’s default Mail application (also referred to as “Mail.app” or “Apple Mail”) has a somewhat checkered past.
