MailTwin
The best AI email assistant for Mac in 2026: an honest roundup
"Best" depends entirely on three questions, so answer them before reading any list — including this one (yes, we make one of these products; the verdicts below are written to survive that bias):
1. Client or layer? Are you willing to move into a new email app, or do you want AI added to the Mail you already use? 2. Where may your mail travel? Through a vendor's cloud (more automation), or only between your Mac and an AI provider you chose (more ownership)? 3. Subscription or purchase? $300–$1,400 a year buys ongoing service; a one-time price buys a tool.
Here are the five serious options for a Mac user in July 2026, each with a straight verdict.
MailTwin’s core workflow: type a few rough reply points and it drafts a complete, editable Apple Mail email in the learned voice for that account. You review every word before insertion; it never auto-sends. Christopher Naas, MailTwin’s maker, says this saves him an hour or more on busy email days — personal experience, not a promised result.
At a glance
| Type | Price (July 2026) | Accounts | AI approach | |
|---|---|---|---|---|
| Superhuman | Replacement client (suite) | ~$33/user/mo annual ($40 monthly) | Gmail, Outlook (as of mid-2026) | Built-in cloud AI |
| Shortwave | Replacement client | $30–$120/seat/mo | Gmail / Google Workspace only | Agentic cloud AI (Claude models) |
| Spark +AI | Replacement client | Free tier; Plus $99/yr; Pro $199/yr | Most providers | Cloud AI (Azure OpenAI), quotas |
| Apple Intelligence in Mail | Built into Apple Mail | Free with macOS | Anything Mail carries | On-device / Private Cloud Compute |
| MailTwin | AI layer on Apple Mail | $19.90 once (5-pack $49.90) | Anything Mail carries | Bring your own: 8 engines, incl. 2 free on-device |
Superhuman — best for teams who want the fastest full client, funded by a work budget
Superhuman remains the reference point for speed: keyboard-first triage, split inbox, follow-up reminders, and AI drafting in a client people genuinely enjoy. Since Grammarly acquired it in 2025 (the combined company took the Superhuman name), it ships as a suite — Mail, Grammarly, Docs, and the Go assistant — and as of July 2026 new customers get Superhuman Mail via the Business plan at about $33/user/month billed annually.
Choose it if: your team lives in email, values shared conversations and CRM integrations, and the company pays. Skip it if: you're an individual balking at ~$400/year, or your mail shouldn't transit a vendor's cloud.
Shortwave — best for Gmail power users who want real AI automation
Shortwave is the most ambitious AI in this list: an assistant that can search, summarize, draft, file, and execute multi-step tasks across your inbox, with plan tiers mapped to Claude models (Haiku through Opus, as of July 2026). The catch is structural: it supports Gmail and Google Workspace only — Outlook, iCloud, and IMAP users are out, barring a forwarding workaround. Paid tiers run $30–$120 per seat per month.
Choose it if: you're all-in on Gmail, drowning in volume, and want AI actively managing the inbox. Skip it if: your accounts aren't Google, or per-seat SaaS pricing for personal email feels wrong.
Spark +AI — best for a free-to-start, cross-platform modern client
Readdle's Spark is a polished client across Mac, Windows, iOS, and Android, with a real free tier. Spark +AI adds compose, rewrites, summaries, and a "My Writing Style" feature, processed in the cloud via Azure OpenAI with monthly quotas — Plus at $99/year, Pro at $199/year as of July 2026. AI is off by default, a respectful choice.
Choose it if: you want one nicer-than-stock email app on every platform and light AI assistance. Skip it if: you want deep voice matching, provider choice, or your mail kept out of vendor clouds.
Apple Intelligence in Mail — best for casual email at zero cost
On a supported Mac, Apple Mail already gives you Smart Reply, thread and message summaries, inbox summary previews, priority messages, and Writing Tools — free, private, no setup. For light correspondence it's quietly excellent. Its limits: a capable-Mac requirement, limited language coverage (16 languages as of mid-2026), one generic voice, no model choice, and no deeper actions (translation, action items, freeform).
Choose it if: your email is light and free-and-built-in beats everything. Skip it if: you write substantial email and want it to sound like you.
MailTwin — best for Apple Mail users who want ownership
Full disclosure: this is our product, so here's the pitch and the caveats in equal measure.
MailTwin is a macOS menubar app that adds AI to Apple Mail rather than replacing it. Its two distinctive ideas: your voice, per account — it learns from your sent mail, locally and only when you explicitly start indexing, keeping work voice and personal voice separate — and bring your own AI: eight engines (Apple Intelligence and Ollama free and on-device; Claude, OpenAI, Gemini, Groq, Grok, DeepSeek by key), with no MailTwin server ever touching mail content. Actions cover reply, reply-in-my-style, summarize, action items, translate, improve draft, and freeform, plus follow-up tracking and a reviewable Inbox Cleanup with receipts and undo. Every rewrite passes an on-Mac validator so numbers, dates, and links can't silently change. $19.90 once, 30-day full trial, 15 languages.
Choose it if: you're staying in Apple Mail, you want replies that sound like you (differently per account), and you prefer owning a tool to renting a service. Skip it if: you love web clients or need mobile — MailTwin is macOS-and-Apple-Mail-only with no mobile app, cloud engines mean managing your own API key (the two on-device engines need none), it has no team features, and it's a v1 product from a small Norwegian developer, not a suite.
How to decide in one minute
- Team + budget + want a new client → Superhuman.
- Gmail-only + maximum automation → Shortwave.
- Cross-platform client + free to start → Spark.
- Light email + zero cost → Apple Intelligence alone.
- Apple Mail + your voice + your AI + one-time price → MailTwin.
FAQ
What's the best free AI email option on a Mac?
Apple Intelligence in Mail, on a supported Mac — Smart Reply, summaries, and Writing Tools at no cost. MailTwin's 30-day trial (and its free on-device engines) let you test the voice-matching layer on top before paying anything.
Which AI email assistants work with Apple Mail?
Apple Intelligence is built in; MailTwin layers on top of it. Superhuman, Shortwave, and Spark are separate clients that replace Apple Mail rather than extend it.
Which options avoid sending mail through a vendor's cloud?
Apple Intelligence (on-device / Private Cloud Compute) and MailTwin (no MailTwin server; content goes directly from your Mac to your chosen provider, or stays on-device with Apple Intelligence or Ollama).
What do these tools cost per year?
As of July 2026: Superhuman ~$396+/user, Shortwave $360–$1,440/seat, Spark $0–$199, Apple Intelligence free, MailTwin $19.90 total (one-time, lifetime 1.x updates).
Can any of them write in my personal style?
Superhuman and Spark offer style-aware drafting in their clouds. MailTwin is the one built around it: locally learned, per-account voice profiles, so work and personal replies each sound like you.
If you're the Apple Mail type
The fastest way to place yourself on this list is to try the layer approach on your real inbox: 30-day full trial, no card, $19.90 once if it earns its keep.