Two things changed in this category and most guides have not caught up. The AI in Gmail and Outlook is now bundled into the Workspace and Microsoft 365 plans many people already pay for. And Superhuman, the premium client this category was built around, was acquired by Grammarly and repriced — its email features now sit behind plans running $25 to $40 a month.
So the useful question is not which assistant writes the best email. It is what you already have, what a paid tool adds on top, and whether that tool actually acts on your inbox or just leaves drafts for you to send. This guide covers six tools in three groups on exactly that basis.
Three kinds of email AI
Built into your email platform. Gemini in Gmail and Copilot in Outlook. Nothing to install, nothing new to learn, and increasingly included in the subscription rather than sold separately.
A replacement email client. Superhuman and Shortwave replace Gmail or Outlook entirely with a faster interface built around keyboard shortcuts, AI drafting and split inboxes. You change where you read email.
A layer on your existing inbox. SaneBox and Fyxer sit on top of Gmail or Outlook without asking you to switch apps. They sort, triage and in some cases draft, but you keep your current client.
The third group is the easiest to trial and the easiest to abandon, because nothing about your setup changes if you stop paying.
What you may already have
Before paying anything, check your existing subscription.
Gemini in Gmail drafts replies, summarises long threads, and offers a “help me write” layer inside the standard Gmail interface. Google has moved these features into Workspace business plans rather than selling them as a separate AI add-on, so many organisations already hold them.
Copilot in Outlook does the equivalent for Microsoft: drafting, thread summaries, and pulling context from across Microsoft 365. The important caveat is that full Copilot is an add-on to a qualifying Microsoft 365 licence rather than something included in every plan, so what you have depends on which licence your organisation bought.
For most people writing a normal volume of email, that is enough. A $30 a month client is a hard sell next to an inbox you already pay for, and it only makes sense at high message volume.
Does it draft, or does it send?
This is the question that matters most and the one almost no comparison asks. Autonomy levels differ sharply, and the vendors are not equally clear about it.
Fyxer states explicitly in its own FAQ that it drafts emails but never sends them. Other tools in this category leave pre-written replies waiting in your inbox for you to review and send. Some agent platforms will act without review if configured to.
For anything client-facing, draft-only is the safer default. An assistant that sends on your behalf can be genuinely useful for routine scheduling replies, and genuinely damaging on a sensitive thread. Read each vendor’s documentation rather than assuming, because the marketing language of “handles your inbox” covers both behaviours.
Replacement email clients
1. Superhuman
Superhuman is the speed product: keyboard shortcuts for everything, split inboxes, instant search and AI auto-drafts written in your voice. For people processing very high message volume it remains the fastest way to work through an inbox.
The ownership and pricing both changed. Grammarly acquired Superhuman on 30 June 2025, in a deal reported at $825 million and completed in October 2025. Grammarly’s parent company subsequently renamed itself Superhuman, so the same name now refers to both the email client and the wider suite — a genuine source of confusion when reading pricing pages.
Current structure, as reported: Superhuman Mail Starter is $30 a month billed monthly, or $25 billed annually. Mail Business is $40 monthly, or roughly $33 annually. Separately, the Superhuman Suite bundles Mail with Grammarly, Coda and Go across Free, Pro, Business and Enterprise tiers — and Mail is not included in the Free or Pro suite tiers, with Pro at around $12 covering Grammarly and Go only.
The practical warning: Mail is priced separately from the Suite, and both have a plan called Business. If a quote looks like it covers everything, confirm whether it is Suite Business or Mail Business. Our Grammarly review covers the writing side of the same suite.
Suits: founders, executives and sales staff processing high volume daily, where triage speed compounds.
2. Shortwave
Shortwave is the Gmail-native alternative, with thread summaries, AI drafting, strong search and automation. It is consistently described as offering comparable AI depth at roughly half Superhuman’s annual cost.
It has a free tier, with two documented catches: AI usage is capped, and free accounts append a “Sent with Shortwave” signature to outgoing mail, which rules the free plan out for professional correspondence. Paid tiers are reported from around $14 to $18 a month, rising to roughly $120 per seat for the top tier.
It is Gmail-only, so Outlook users can stop reading here.
Suits: Gmail users who want an AI-native client without Superhuman pricing.
Layers on your existing inbox
3. SaneBox
SaneBox is the oldest approach here and does one job: it filters. Unimportant mail is moved out of the inbox into folders you review later, learning from what you actually open and answer. It works with essentially any email provider because it operates at the mail-server level rather than as an app.
It is not an AI assistant in the modern sense, and it is worth being clear about that: no drafting, no summarisation, no reply suggestions. If your problem is volume rather than writing, that focus is the point.
Pricing is reported from around $7 a month, dropping to roughly $4.54 on two-year billing, and rising to about $36 for higher tiers. It is among the cheapest tools in this guide.
Suits: people whose problem is inbox noise rather than writing, and who do not want to change email clients.
4. Fyxer AI
Fyxer sits on top of Gmail or Outlook, sorting the inbox into categories, drafting replies in your writing style and taking meeting notes. It is the closest thing here to a delegated assistant that does not require switching clients.
Pricing is reported between roughly $22.50 and $30 per user per month depending on billing and source. As noted above, Fyxer documents that it drafts but does not send, which is worth knowing in both directions: safer for client work, less autonomous than the marketing implies.
Reported limitations include mail occasionally landing in the wrong category, and trial billing that has surprised some users, so check the renewal terms.
Suits: professionals who want drafting and triage without leaving Gmail or Outlook.
Built into your platform
5. Gemini in Gmail
Drafting, rewriting, tone adjustment and thread summarisation inside Gmail itself, with no separate app. Google has folded these capabilities into Workspace business tiers rather than charging a distinct AI fee, which makes it the cheapest capable option for most Workspace customers — effectively free at the point of use.
What it lacks is the triage layer. It helps you write; it does not decide what deserves your attention.
6. Microsoft Copilot in Outlook
The Microsoft equivalent, with the advantage of context from across Microsoft 365: documents, calendar and Teams alongside mail. For organisations already standardised on Microsoft, that context is the differentiator.
The cost structure is less simple than Google’s. Full Microsoft 365 Copilot is a per-user add-on on top of a qualifying licence rather than an inclusion, so confirm what your organisation actually holds before assuming access. Our guide to AI productivity tools covers the wider Microsoft AI packaging.
Comparison
Reported figures from vendor pages and current analysis. Where a figure varies by source, a range is shown.
| Tool | Type | Platform | Free tier | Paid entry | Drafts or sends? |
|---|---|---|---|---|---|
| Gemini in Gmail | Built in | Gmail | Included in Workspace tiers | No separate AI fee | Drafts |
| Copilot in Outlook | Built in | Outlook | Varies by licence | Add-on to M365 | Drafts |
| Superhuman | Replacement client | Gmail, Outlook | None for Mail | $25 annual / $30 monthly | Drafts |
| Shortwave | Replacement client | Gmail only | Yes, capped AI + signature | ~$14–18 | Drafts |
| SaneBox | Inbox layer | Almost any provider | Trial only | ~$7, or ~$4.54 on 2-year | Neither — filters only |
| Fyxer AI | Inbox layer | Gmail, Outlook | Trial only | ~$22.50–30 | Drafts, never sends |
There is no writing-quality column. No vendor publishes a reproducible measure of draft quality, and most of these tools route to the same underlying frontier models, so the differentiator is triage and workflow rather than prose.
The entry-tier trap
One pattern runs through this category and costs people money: the advertised entry tier is frequently not the tier containing the AI features you want.
Superhuman is the clearest example, where the Suite Pro plan at around $12 does not include Mail at all. Shortwave’s free tier caps AI and brands your outgoing mail. Microsoft’s AI is an add-on rather than an inclusion on most licences.
Before subscribing, confirm three things: which named plan contains the specific feature you are buying for, whether the price you were quoted is monthly or annual, and what the renewal terms are after a trial. Several tools here run trials that convert automatically.
How to choose
Check your existing plan first. If you have Workspace or Microsoft 365, you may already have drafting and summaries at no extra cost.
Your problem is volume, not writing: a filtering layer costs a fraction of a full client and does not require changing anything.
You live in your inbox all day: a replacement client is where the time savings compound, and the premium is easier to justify above roughly 50 messages a day.
You want drafting without switching apps: an inbox layer sits on Gmail or Outlook and leaves your setup intact.
You are on Outlook: several tools here are Gmail-only, which narrows the field before any other consideration.
You handle confidential correspondence: check where mail is processed and whether it is used for training, and prefer draft-only behaviour over anything that sends autonomously.
Related guides
- Best AI Writing Tools in 2026
- Grammarly Review 2026
- Best AI Productivity Tools in 2026
- Best AI Meeting Assistants in 2026
- Best AI CRM Tools in 2026
- Best AI Chatbots in 2026
Frequently asked questions
Do I need to pay for an AI email assistant?
Often not. Gemini is included in Google Workspace business tiers and Copilot is available on Microsoft 365, so drafting and summaries may already be covered. Paid tools add triage, speed and delegation rather than better writing.
What happened to Superhuman?
Grammarly acquired it on 30 June 2025, with the deal reported at $825 million and completed that October. Grammarly’s parent then renamed itself Superhuman, so the name now covers both the email client and the wider suite. Mail plans are reported at $25 to $40 a month depending on tier and billing.
Will these tools send email for me?
Usually not by default. Fyxer states in its FAQ that it drafts but never sends, and several tools leave replies waiting for your approval. Autonomy differs by product, so check the documentation rather than the marketing.
Which has a genuinely usable free tier?
Shortwave, with two caveats: AI usage is capped and free accounts append a “Sent with Shortwave” signature to outgoing mail. The platform-native options are free at the point of use if your organisation already holds the relevant plan.
Which works with Outlook?
Copilot, Superhuman, SaneBox and Fyxer. Shortwave is Gmail-only, and Gemini’s email features are tied to Gmail.
Is a faster email client worth $30 a month?
It depends on volume. The case rests on triage speed compounding across a heavy inbox, which is why these products target people processing dozens of messages daily. At normal volume, the free option in your existing plan is difficult to beat on value.
Conclusion
Start with what you already pay for. Drafting and thread summaries now come with Google Workspace and are available on Microsoft 365, and for most people that covers the writing problem entirely.
Pay for a dedicated tool when the problem is something those do not solve: triage at volume, keyboard-speed processing, or delegated drafting inside your existing inbox. Then check two details before subscribing — which named plan actually contains the feature you want, and whether the tool drafts for your approval or acts on its own. Those two answers matter more than any comparison of writing quality.
