# Build Your Own Superhuman Alternative - Tool: Build Your Own SaaS Alternative - Last updated: May 2026 ## TL;DR Superhuman is the most expensive email client on the market at $30/user/mo Starter — $3,000/yr for 10 seats just for keyboard shortcuts and AI email. Grammarly acquired it in July 2025 for an estimated $300–500M, making the roadmap uncertain. Gmail and Outlook only — no Fastmail or IMAP. Building a vertical AI-powered email client costs $120K–$280K and takes 4–6 months. The real angle is verticalized AI-email, not replicating Superhuman's brand. ## Frequently asked questions ### How much does it cost to build a Superhuman alternative? Building a Superhuman alternative costs $120K–$280K for an MVP with Gmail/Outlook integration, local email caching, keyboard shortcuts, AI drafting, and snooze/follow-up features. Using Mailspring's open-source Electron + SQLite architecture as a foundation reduces scope by 4–6 weeks. The native macOS app adds $30–50K if required. ### How long does it take to build a Superhuman clone? 4–6 months for a web + desktop client with Gmail/Outlook integration, AI drafting, and core productivity features with a team of 3. The Gmail API integration and local cache architecture take 5–7 weeks. The 'feel of speed' — sub-100ms keyboard interactions — requires an additional 2–3 weeks of performance tuning after the core features are built. ### Are there open-source Superhuman alternatives? Two notable options: Mailspring (~17.5K GitHub stars, GPLv3) is the strongest — an Electron + React email client with Gmail, Outlook, iCloud, and IMAP support, read receipts, and an active development community. Version 1.21.1 was released in May 2026. Thunderbird Android (~9K stars, MPL-2.0) offers the broadest provider support. Neither includes AI drafting out of the box. ### Can RapidDev build a custom Superhuman alternative? Yes — RapidDev has built 600+ applications including AI-powered productivity tools and email integration platforms. We recommend focusing on a specific vertical use case (sales, legal, support) rather than building a horizontal Superhuman clone. Visit rapidevelopers.com/contact for a free consultation. ### Does Superhuman support IMAP or non-Gmail providers? No — Superhuman officially supports only Gmail (personal and Google Workspace) and Microsoft Outlook/Exchange. There is no IMAP support, no Fastmail, no iCloud, no ProtonMail. This is a deliberate product decision that significantly limits Superhuman's addressable market and is cited in reviews as the primary reason teams consider alternatives. ### What does Grammarly's acquisition mean for Superhuman users? Grammarly acquired Superhuman on July 1, 2025 (TechCrunch). In October 2025, Grammarly renamed its parent company to 'Superhuman.' The strategic rationale is integrating Superhuman's AI email features with Grammarly's AI writing technology. For users, this means the product roadmap is now driven by Grammarly's broader AI writing strategy, not by email-specific power user needs. Features like shared inbox, IMAP support, and advanced keyboard customization may be deprioritized in favor of Grammarly AI integration features. ### What is the hardest part of building a Superhuman alternative? The local-first email caching architecture is the hardest engineering challenge — building a SQLite cache that synchronizes reliably with Gmail's API, handles incremental syncs, manages token refresh, and provides sub-100ms inbox loading requires careful architecture. The Gmail API's rate limits (250 quota units per second per user) and partial response patterns require intelligent caching to avoid hitting limits during full inbox sync. ### Can I build a shared inbox on a Superhuman alternative? Yes — and this is one of the strongest differentiators since Superhuman offers no shared inbox on any plan. Implement shared inbox as a virtual mailbox layer: incoming emails to the shared address are stored in a shared queue in PostgreSQL, with assignment rules, collision detection (prevent two agents from replying simultaneously), internal notes, and SLA tracking. This covers the use case that drives teams to Help Scout or Intercom. --- Source: https://www.rapidevelopers.com/clone/superhuman © RapidDev — https://www.rapidevelopers.com/clone/superhuman