Which AI should I use to write my emails?
Updated · 10 min read · by the HidenGPT team
Start with the AI already inside the inbox you use. Gmail's Help me write runs on Gemini with an eligible Google plan, and Copilot drafts in Outlook with Microsoft 365 Personal, Family or Premium. Pick an inbox app like Superhuman or Shortwave if email is most of your day, a chatbot like ChatGPT or Claude for one hard message, and HidenGPT, which we make, for a subject line, a spam-word check and a voice built from your own emails.
Whichever you pick, the reply works when you give it the facts: who it's to, what you want and by when.
Disclosure: we make HidenGPT, one of the tools below. The facts for every tool come from its own website, read on October 15, 2026, with links; we didn't blind-test them. If something has changed, tell us through the contact page.
| Tool | Where it writes | What you need |
|---|---|---|
| Gemini in Gmail | Inside Gmail's compose window | An eligible Google Workspace or Google AI plan; personal accounts in the US only; 18+ |
| Copilot in Outlook | Inside Outlook on Windows, Mac, web, iOS and Android | Microsoft 365 Personal, Family or Premium; at work, ask your IT admin |
| Grammarly | In the browser and apps where you type | A $0 account; rewrites and tone changes need Pro |
| ChatGPT | In a separate chat; you copy the email out | A $0 account; Plus for more uploads and memory |
| Claude | In a separate chat; Pro adds Claude for Outlook | A $0 account; Pro for Outlook |
| HidenGPT | In its own composer; you copy the email out | A Pro or Pro Max plan, or 2 trial drafts a day |
| Superhuman Mail | A full email app on top of Gmail or Outlook | A paid plan, from $25 a month billed annually |
| Shortwave | A full email app for Gmail and Google Workspace | A $0 plan with limited AI; Pro for personalized writing |
The tools, side by side
01Gemini in Gmail (Help me write)
Gmail's drafting feature, powered by Gemini, that writes a new email from a prompt or refines one you started.
- Good for
- Gmail users who want help without leaving the compose window. You can ask for a new draft, or refine yours with Formalize, Friendly or Shorten, or type your own instruction. Google says it uses details from your other emails and Drive files to personalize drafts.
- Limits
- Needs an eligible Google Workspace or Google AI plan, and for personal accounts it is restricted to the US. Google AI plans are for ages 18+. Google warns it may suggest inaccurate information.
- Price
- Google AI Plus: $4.99/month (includes Gemini in Gmail). Google AI Pro: $19.99/month. Google AI Ultra: from $99.99/month.
- Sources
- Gmail Help: Write emails with Gemini in Gmail (checked October 15, 2026) · Google AI plans (US) (checked October 15, 2026)
02Microsoft Copilot in Outlook
The AI assistant in Outlook that drafts an email from a prompt and adjusts its tone and length.
- Good for
- Outlook users. It works in new and classic Outlook for Windows, Outlook for Mac, iOS and Android. On mobile, Coaching by Copilot gives feedback on an email you wrote yourself once it has at least 100 characters.
- Limits
- In new Outlook and on the web, drafting with Copilot doesn't support plain-text emails, so you switch the compose format to HTML. Microsoft 365 Basic has no AI features, and on Family and Premium the AI is for the subscription owner only.
- Price
- Microsoft 365 Personal: $9.99/month or $99.99/year. Family: $12.99/month or $129.99/year. Premium: $19.99/month or $199.99/year.
- Sources
- Microsoft Support: Draft an email message with Copilot in Outlook (checked October 15, 2026) · Microsoft 365 plans (US) (checked October 15, 2026)
03Grammarly
A writing assistant that checks and rewrites text through its browser extension and its desktop and mobile apps.
- Good for
- Fixing an email you wrote yourself before you hit send. The $0 plan catches mistakes and shows how your tone comes across; Pro adds full-sentence rewrites and tone adjustment.
- Limits
- AI prompts are capped at 100 a month on Free and 2,000 per member on Pro. Tone adjustment and rewrites are Pro only. The plans page doesn't say which apps each plan covers.
- Price
- Free: $0. Pro: $30/month billed monthly, $60 a quarter, or $144/year.
- Sources
- Grammarly plans page (checked October 15, 2026) · Grammarly Support: How much does Grammarly Pro cost? (checked October 15, 2026)
04ChatGPT
OpenAI's general chatbot. You paste the thread or your notes and ask for a reply.
- Good for
- One difficult email you want to think through: a refusal, a complaint, a message to someone senior. You can ask for three versions at different levels of firmness and pick one. Text chats are unlimited on the $0 plan within OpenAI's abuse guardrails.
- Limits
- It doesn't sit in your inbox, so you copy text in and out. Free has limited uploads, memory and context. Anything you paste goes into a chat, so leave out details you wouldn't share.
- Price
- Free: $0/month. Plus: $20/month. Go and Pro: see their pricing page.
- Sources
- ChatGPT pricing page (checked October 15, 2026)
05Claude
Anthropic's AI assistant for writing and research, with an Outlook add-in on paid plans.
- Good for
- Long or delicate emails where you want to explain the background first. Memory and up to 5 projects are on the $0 plan. Pro adds Claude for Microsoft 365 and Outlook.
- Limits
- Free doesn't include the Outlook or Microsoft 365 integration. Usage limits apply on every plan and reset on a 5-hour session.
- Price
- Free: $0. Pro: $20/month billed monthly, or $17/month billed annually ($200 up front). Max: from $100/month.
- Sources
- Claude pricing page (checked October 15, 2026)
06HidenGPTours
An AI ghostwriter whose Email format drafts cold emails, follow-ups, newsletters, announcements, business emails, thank-you notes, apologies and invitations.
- Good for
- Emails where the subject line and wording matter. Each draft opens with a subject aimed at under 50 characters, asks for one thing, flags wording that tends to trip spam filters and can suggest 3 alternative subject lines. Lengths run from 50 to 600 words, and it can write in a voice built from 2-5 of your own emails.
- Limits
- No free plan; the homepage allows 2 trial drafts a day without an account. It doesn't connect to Gmail or Outlook or read your inbox: you type the context in and copy the email out. Nobody can promise where an email lands; that also depends on your sending domain.
- Price
- Pro: $19/month ($3 the first month). Pro Max: $29/month ($9 the first month). Yearly: $68.40 (Pro) or $104.40 (Pro Max).
- Sources
- HidenGPT email writer page (checked October 15, 2026) · HidenGPT pricing page (checked October 15, 2026) · HidenGPT FAQ (checked October 15, 2026)
07Superhuman Mail
A paid email app for people and teams on Gmail or Outlook, with AI that drafts emails and can send them for you.
- Good for
- People who spend hours a day in email and want one app for writing, sorting and scheduling. Starter includes Superhuman AI; Business adds auto drafts, Ask AI and CRM integrations.
- Limits
- No $0 plan was listed on the pricing page, and we saw no trial mentioned on the pages we read. The pages we read don't say whether drafts follow your own writing style.
- Price
- Starter: $30/month billed monthly, or $25/month billed annually. Business: $40/month billed monthly, or $33/month billed annually. Enterprise: contact sales.
- Sources
- Superhuman Mail pricing page (checked October 15, 2026) · Superhuman Mail product page (checked October 15, 2026)
08Shortwave
An AI email app built for Gmail and Google Workspace accounts.
- Good for
- Gmail users who want replies in their own style. Shortwave says its AI learns your voice and style from the emails you send. Personalized AI writing, autocomplete and instant summaries are on Pro.
- Limits
- It connects natively only to Gmail and Google Workspace; Outlook, Yahoo and others work by first connecting them to a Gmail account. The $0 plan has a limited AI quota, 90 days of search history and a "Sent with Shortwave" signature.
- Price
- Free: $0. Pro: $18/seat/month. Business: $30, Premier: $45, Max: $120 per seat/month. Paid plans start with a 14-day trial.
- Sources
- Shortwave pricing page (checked October 15, 2026) · Shortwave homepage (checked October 15, 2026)
How to choose: start from where you write
Most people never need a new app. If your mail is in Gmail and you already pay for a Google AI plan, try Help me write first. If you have Microsoft 365 Personal, Family or Premium, Copilot is already in Outlook. Check those two before you pay for anything else.
Look further when one of three things is true. You write a lot of email every day and want sorting, scheduling and drafting in one place: that is what Superhuman and Shortwave sell. You have one hard email to get right and want to talk it through: a chatbot is better at that than a compose-window button. Or you need a specific format, such as a cold email under 120 words with a subject line you can test: that is where a dedicated writer helps.
What to give any AI before it writes
A short brief beats a long prompt. Before you ask for a draft, write four lines: who it's to and how well you know them, the one thing you want them to do, the deadline or date, and one fact only you know, such as the order number or the name of the person who referred you.
Then add one sentence on tone, in plain words: "friendly, like a colleague I see every week" or "polite but firm, this is the second time". Paste the email you're replying to if there is one. The AI will still miss things, but it won't have to guess the parts that matter.
Example: the brief and the email it should produce
Example brief: "To Dana, the office manager I met once. Our team needs the large meeting room on Thursday 12 November from 2 to 4 pm for a client visit. I booked it in the calendar but it shows a conflict with the finance review. Ask if finance can move to the small room. Polite, short."
Example email, about 75 words:
"Subject: Large meeting room, Thursday 12 Nov, 2 to 4 pm
Hi Dana,
We have a client visiting on Thursday 12 November and I booked the large meeting room from 2 to 4 pm. The calendar shows a clash with the finance review in the same slot.
Would finance be able to use the small room that afternoon? We need the screen and the seats for eight people.
Thanks for sorting this out, Sam"
Check any draft against that standard: the subject names the date, the ask comes in the second paragraph, and there is one request.
Where HidenGPT is weaker for email
We make HidenGPT, so here is where it falls short. It doesn't live in your inbox: Gemini, Copilot, Superhuman and Shortwave can see the thread you're answering, while HidenGPT only knows what you type into it. There's no free plan, only 2 trial drafts a day on the homepage, and it doesn't send, schedule or sort mail.
Where it differs: each email type has its own rules, the subject line length and spam-prone wording are checked after drafting, and the red pen removes stock phrases before you see the draft.
How we checked
We read each vendor's own pricing, help and product pages on 15 October 2026 and linked them under each entry. We did not test output quality side by side, and the order is not a ranking.
Prices are in US dollars. Where a page didn't say something, such as whether Superhuman drafts in your style, we say so instead of guessing. If something has changed, tell us through the contact page.
Common mistakes
- Asking for "a professional email" with no facts: give the name, the ask and the date, or the AI will invent filler.
- Sending the first draft unread: check names, dates and numbers, which is where AI drafts most often go wrong.
- Letting the reply grow longer than the email you got: match its length, or go shorter.
- Pasting private details into a chatbot you don't control: remove account numbers and anything about other people first.
- Paying for a new app before trying the AI already in Gmail or Outlook: check what your current plan includes.
Questions
Is there a free AI for writing emails?
Yes, several tools have a $0 plan with limits. ChatGPT, Claude, Grammarly and Shortwave all list one. Gemini in Gmail needs an eligible Google plan, Copilot in Outlook needs Microsoft 365 Personal, Family or Premium, and HidenGPT has no free plan, just 2 trial drafts a day.
Does Gmail have AI that writes emails?
Yes, Help me write drafts and refines emails in Gmail using Gemini. Google says it needs an eligible Google Workspace or Google AI plan, and for personal accounts it is available in the US only.
How do I get Copilot to write emails in Outlook?
In new Outlook, select the Copilot icon, choose Draft and type what you want to say. You then adjust the tone or length from the options, or retry. It needs a Microsoft 365 plan with AI features; Basic doesn't have them.
Can AI write emails in my own style?
Some tools try. Shortwave says its AI learns your style from the emails you send, Gmail's Help me write uses your other emails and Drive files to personalize drafts, and HidenGPT builds a voice from 2-5 samples of your writing. With ChatGPT or Claude, paste two or three of your emails as examples.
Is it OK to use AI to write work emails?
Usually yes, as long as your employer's rules allow it and you check every draft. You are still the sender, so read it, fix anything untrue and keep confidential details out of tools your company hasn't approved.
Which AI is good for cold emails?
Any of them can draft one, but you need a specific first line and one small ask. HidenGPT's email format keeps cold emails near 120 words and flags spam-prone wording; with a chatbot, give it a word limit and the recipient's name and company.
Can AI reply to emails automatically?
Some inbox apps go that far. Superhuman says its AI can draft and, if you want, send emails for you, and its Business plan lists auto drafts. Gmail's and Outlook's built-in tools draft, and you send.
Sources
- Gmail Help: Write emails with Gemini in Gmail (checked October 15, 2026)
- Google AI plans (US) (checked October 15, 2026)
- Microsoft Support: Draft an email message with Copilot in Outlook (checked October 15, 2026)
- Microsoft 365 plans (US) (checked October 15, 2026)
- Grammarly plans page (checked October 15, 2026)
- Grammarly Support: How much does Grammarly Pro cost? (checked October 15, 2026)
- ChatGPT pricing page (checked October 15, 2026)
- Claude pricing page (checked October 15, 2026)
- Superhuman Mail pricing page (checked October 15, 2026)
- Superhuman Mail product page (checked October 15, 2026)
- Shortwave pricing page (checked October 15, 2026)
- Shortwave homepage (checked October 15, 2026)
- HidenGPT email writer page (checked October 15, 2026)
- HidenGPT pricing page (checked October 15, 2026)
- HidenGPT FAQ (checked October 15, 2026)