The short answer
The best AI for writing emails in 2026 is the one inside your inbox. For Gmail, Google's Gemini is our pick: Google AI Plus adds Gemini in Gmail, and Google AI Pro adds Gemini 4 Argon and Docs. For Outlook, Microsoft Copilot works in Outlook on Microsoft 365 Personal, Family, Premium and Pro. The best free option is Anthropic's Claude, whose Gmail connector works on the free plan and asks for approval before sending.
| Our pick | Gemini in Gmail (Google AI Plus or Pro) |
|---|---|
| Runner-up | Microsoft Copilot in Outlook (Microsoft 365 plans) |
| Best free | Claude Free with the Gmail connector |
| Also good | ChatGPT Gmail plugin (sending on Plus and up); Grammarly for checking tone |
| Keep human | Bad news, legal or money commitments, first contact with someone important |
| Check first | Training settings on personal accounts |
The best AI for writing emails in 2026, in one paragraph
The best AI for email is the one that already sits inside your inbox, because the slow part of email is not typing but reading the thread, working out what is being asked and finding the right tone. Copying a thread into a separate chat window and pasting the answer back costs most of the time you hoped to save. So our pick depends on where your mail lives. If you use Gmail, Google's Gemini is our pick: from the Google AI Plus plan upwards it works inside Gmail, and Google AI Pro adds Docs and the flagship Gemini 4 Argon model. If you live in Outlook, Microsoft Copilot is the runner-up and the right answer for you. If you want to pay nothing, Anthropic's Claude on its free plan can connect to Gmail, read threads and draft replies, and asks for your approval before it sends anything.
| Our pick: Gemini | Runner-up: Microsoft Copilot | Best free: Claude Free | |
|---|---|---|---|
| Works inside | Gmail from Google AI Plus; Docs from Google AI Pro | Outlook on Microsoft 365 Personal, Family, Premium and Pro; Outlook at work with a Microsoft 365 Copilot licence | Gmail, Google Calendar and Google Drive through connectors, on every plan |
| Model | Flash on AI Plus; Gemini 4 Argon on AI Pro and Ultra | Chosen by Microsoft; not named per plan for consumers | Claude Sonnet 5.5 and Claude Haiku 5.5 on Free |
| Sends for you | You stay in Gmail and press send yourself | You review in Outlook | Asks for approval before sending by default |
| The catch | The free Gemini app does not work inside Gmail | Two different Copilots with different privacy rules | Usage limits every 5 hours and every week |
Our pick: Gemini in Gmail
Why. Gemini is Google's AI assistant, and on paid Google AI plans it appears inside Gmail itself. You can ask it to summarise a long thread, draft a reply or pull a figure from a file in Drive without leaving the message you are answering. Google's plans page lists Gemini in Gmail from Google AI Plus, the cheapest paid plan, which uses the Flash model and gives twice the free limits. Google AI Pro adds Gemini in Docs, four times the free limits, the 1 million token context window and Gemini 4 Argon, the flagship model Google made available to Pro and Ultra subscribers from 13 October 2026. For most people who answer a lot of email, AI Plus is enough; pick Pro if you also write long documents.
Who it suits. Anyone whose working day runs through Gmail, Google Calendar and Drive: freelancers, small business owners, recruiters and account managers who send dozens of replies a day. It is especially good for the reply that needs a fact from somewhere else, such as a date from your calendar or a number from a Drive file.
The catch. The free Gemini app is a separate chat app, not Gmail help, and since 9 October 2026 most free prompts are answered by the smaller Flash-Lite model. Privacy also needs a minute of your time. On personal Google accounts with Keep Activity switched on, Google uses your activity to improve its services, including model training, and human reviewers read some chats. You change this at myactivity.google.com/product/gemini. If your employer gives you Gemini through Google Workspace, use that account for anything confidential: Google says Workspace content is not reviewed by humans or used for training outside your organisation without permission. Read our full Gemini guide for the plan details.
Runner-up: Microsoft Copilot in Outlook
Why. If your inbox is Outlook, Copilot is the assistant that lives where you work. Microsoft's pricing page lists Copilot in Word, Excel, PowerPoint and Outlook on Microsoft 365 Personal (in the desktop apps) and on Family, Premium and Pro, with more usage on Premium and Pro. At work, a Microsoft 365 Copilot licence lets Copilot draw on your organisation's mail, files and Teams meetings under enterprise data protection, which is the strongest privacy position of any option on this page. That matters for email, because the best reply often depends on what was said in a meeting last week.
Who it suits. People in companies that run on Microsoft 365, and households already paying for Microsoft 365 Personal or Family. Note that on the Family plan the Copilot features only work for the subscription owner, not the other five people.
The catch. There are really two Copilots. The work version, signed in with a Microsoft Entra account, does not use your prompts, responses or company data to train foundation models. The personal app was rebuilt on 18 August 2026, and Microsoft has not clearly documented whether it trains on your conversations, so keep client mail out of it. Microsoft also does not name the models behind personal plans. Our Copilot guide covers both versions.
Best free option: Claude with the Gmail connector
Why. Claude is Anthropic's AI assistant, and Anthropic's help centre says its Gmail, Google Calendar and Google Drive connectors are available to all users, including Free. Once connected, Claude can read and draft email, check your calendar and read Drive files, and it asks for your approval before sending email by default. The free plan runs on Claude Sonnet 5.5 and Claude Haiku 5.5, and Claude is strong at the part of email most tools get wrong: a reply that is polite, firm and short at the same time. If you prefer to keep AI away from your inbox entirely, you can still paste a thread into a normal chat.
Who it suits. Gmail users who want AI help without a subscription, and anyone who writes sensitive replies (pushing back on a client, declining a request, chasing a late invoice) where tone matters more than speed.
The catch. The free plan has limits that reset every 5 hours with a weekly cap, so a heavy email day can run out. On Free, Pro, Max and Ultra your chats can be used to train Anthropic's models unless you turn off Help Improve our AI models under Settings, then Privacy. The Microsoft 365 connection, for Outlook users, starts on the Pro plan. See our Claude guide and the Claude vs Gemini comparison if you are choosing between the two for Google work.
Also worth knowing
ChatGPT, from OpenAI, has Gmail, Google Calendar and Google Contacts plugins, can connect several Google accounts at once on Plus, Pro, Business and Enterprise since 28 August 2026, and can send email from a chat on the web on Plus and above, so it is a fair choice if you already pay for it (see ChatGPT vs Claude). Grammarly is not a drafting tool first, but its free plan checks grammar, spelling and tone in Outlook, in Google Docs and in your browser, with 100 AI prompts a month. Its training setting is on by default for individual accounts; our Grammarly guide shows where to switch it off.
How to choose: three questions
- Where does your email live? Gmail points to Gemini on Google AI Plus or Pro, or Claude Free if you will not pay. Outlook points to Copilot. If you use both, pick the assistant for the inbox that carries your most important mail.
- Is it work mail with confidential content? Then use the version your employer provides: Gemini through Google Workspace or Microsoft 365 Copilot through your work account. Both keep your content out of model training by default. Do not paste client threads into a personal account with training switched on.
- Do you want drafts or do you want it to act? For drafting, every tool here works. For reading many threads, finding the ones that need you and preparing replies in one go, you need a connector or built-in assistant (Gemini in Gmail, Copilot in Outlook, Claude's Gmail connector, ChatGPT's Gmail plugin), and you should keep approval before sending switched on.
A workflow for writing emails with AI, end to end
Here is how one reply goes from an awkward thread to a sent message in about three minutes. The example is a client who wants extra work added to a project without changing the deadline.
- Get the ask in plain words. Open the thread and ask the assistant to summarise it in three lines and state exactly what is being asked of you, by when. This catches the request buried in the fourth reply.
- Decide your answer yourself. This is the step to keep human. Decide what you will agree to and what you will refuse. In the example: yes to the extra page, no to the same deadline, offer two more days.
- Give the decision and the constraints. Tell the assistant your decision, the tone (warm, firm), the length (under 120 words) and one thing it must include (the new date). Constraints are what turn a generic draft into your email.
- Ask for two versions. One warmer, one more direct. Picking between two drafts is faster than editing one.
- Check every fact. Names, dates, amounts and attachments. AI drafts invent plausible details, such as a meeting day or a percentage, and these are the errors that embarrass you.
- Read it aloud once, then send it yourself. If a sentence sounds like nobody you know, cut it. Keep approval before sending on in any tool that can send.
- Save what works. When you find instructions that produce your voice, save them. Gemini is replacing Gems with skills: personal Gems become read-only on 17 November 2026 and are converted to skills automatically. In Claude, put the instructions in a Project.
What to keep human in your email
Three kinds of email are worth writing yourself or rewriting heavily: anything that delivers bad news to a person (a rejection, a redundancy, a complaint reply that admits fault), anything with legal or financial commitments, and the first email to someone important. AI is excellent at structure and tone, but the reader can usually tell when nobody really thought about them. A good rule is to let AI write the draft and the subject line, then make one change only you could make: a specific detail from your last conversation, or a sentence about what happens next.
Want more? Our prompt library for emails has more templates, and how to write a good prompt explains why the constraints in step 3 matter so much.
Prompts for writing emails with AI
These seven prompts work in Gemini, Copilot, Claude or ChatGPT. Replace everything in [square brackets]. The ones that read your inbox need a connector or a built-in assistant; otherwise, paste the thread in.
Prompts to copy
Find the real ask in a long thread
Read this email thread and tell me in three lines: what is being asked of me, by whom, and by when. Then list anything I promised earlier in the thread that I have not done yet. [paste thread or name the thread]
You get: The request and your open promises, before you reply
Say yes to one thing and no to another
Draft a reply to [name] that agrees to [what you accept] but declines [what you refuse], and offers [your alternative]. Tone: warm but firm. Under 120 words. No apologies beyond one sentence. Give me two versions, one warmer and one more direct.
You get: Two ready drafts that hold your line politely
Chase a late payment without souring things
Write a polite second reminder to [client] about invoice [number] for [amount], due on [date] and now [days] days late. Mention the original due date, ask for a payment date by [day], and offer a short call if there is a problem. Under 100 words. Subject line included.
You get: A reminder that gets a date back, with a subject line
Turn notes into a follow-up email
Here are my notes from a meeting with [names] about [topic]: [paste notes]. Write a follow-up email with a two-line recap, a list of decisions, a list of next steps with owner and date, and one open question. Flag anything in my notes that is unclear instead of guessing.
You get: A clean follow-up with owners and dates, gaps flagged
Triage my inbox
Look at my unread emails from the last [2 days]. Group them into: needs my reply today, needs a reply this week, read only, and can be archived. For the first group, give one line on what each sender wants and draft a reply of under 80 words for each. Do not send anything.
You get: A sorted inbox and draft replies waiting for your approval
Make my draft shorter and clearer
Here is my draft email: [paste draft]. Cut it to [half] its length without losing any request or date. Put the main ask in the first sentence. Keep my wording where it is already clear, and list every change you made so I can check it.
You get: A tighter version and a list of what changed
Write in my voice from now on
Here are five emails I wrote that sound like me: [paste emails]. Describe my style in a short list: sentence length, greeting and sign-off, words I use and avoid, how direct I am. Turn that list into instructions I can save and reuse whenever I ask you to draft an email.
You get: Reusable voice instructions to save as a skill or Project