The best AI email writer is the one that sits where you write your email and hands you a draft you would send. If you live in Gmail, start with Gemini in Gmail. In Outlook, start with Microsoft Copilot. If you want the whole email written from a few facts, in your own voice, try Hemmingway, which is ours: its model came first in our own blind test of email and message writing. If you would rather write it yourself and have it tidied, use Grammarly.
Two questions settle most of it. Where do you write your email? And do you want it written for you, or polished? Some tools start from what you want to say and write the email. Others start from your draft and improve it. If the hard part is starting, you want the first kind.
The short answer
| Tool | What it is | Good for | Watch out for |
|---|---|---|---|
| Hemmingway | Our writing app, with a free email writer tool | A whole email from a few facts, in your voice. Replies drafted from your inbox | Its own app, not a button inside Gmail or Outlook. English-first |
| Gemini in Gmail | Google's assistant inside Gmail | Drafting and replying without leaving Gmail | We have not tested it |
| Microsoft Copilot in Outlook | Microsoft's assistant inside Outlook | Drafts in a tone and length you choose, and summaries of long threads | We have not tested it. Listed with Microsoft 365 plans |
| Grammarly | A writing assistant that works across apps and browsers | Polishing your own draft | Built around checking what you wrote. We have not tested it |
| Superhuman Mail | An email app with AI drafting | Teams on Gmail or Outlook who want a faster inbox | You move to a new mail app. We have not tested it |
| ChatGPT | OpenAI's general assistant | Pasting in the facts and getting a short email back | Scored low on sounding like a person in our tests |
The tools, one at a time
Hemmingway
You say who the email is for and what you want said, and Hemmingway writes it. You get one version with nothing around it to cut. The quickest way in is the free AI email writer: fill in a short form and the email is written in the chat. To answer an email you have received, use the email reply generator.
In the app you can tell it who people are, so it writes to your boss, a client or your sister the way you would. In the apps for Mac, Windows and Android, Inbox connects to Gmail and Outlook and drafts each reply for you to read and send. How that works.
Gemini in Gmail
Google says Gemini in Gmail can write an email from a prompt, turn rough notes into an email that is ready to send, suggest replies that fit the thread, and sum up long conversations. It can also pull in details from your Drive files. If all your mail is in Gmail, its advantage is plain: it is already in the compose window.
Microsoft Copilot in Outlook
Microsoft says Copilot in Outlook can draft emails in the tone and length you ask for, adjust the tone of a draft, and summarise long threads. Microsoft lists it with its Microsoft 365 plans.
Grammarly
Grammarly is best known for checking what you write as you write it. Its site also describes an email writer that produces a draft from a few details and lets you adjust formality, tone and length. It runs as a browser extension and as desktop and mobile apps, so it follows you between sites. It suits people who mostly write their own email.
Superhuman Mail
Superhuman Mail is a whole email app, not an add-on. Its site describes drafts written for you from the context in your inbox, along with sorting and follow-up reminders, and says it is built for teams that use Gmail or Outlook. It makes sense if email is most of your day and you are willing to change the app you read it in.
ChatGPT
ChatGPT is not an email tool, but it works as one: paste in the facts, ask for an email, copy it back. In our tests its model, GPT-6 Astra, wrote short messages and almost never wrapped them in notes, so what you get can be used as it is. It scored lower than Hemmingway-1 and Claude's models on sounding like a person. Hemmingway vs ChatGPT.
What our tests cover, and what they do not
CommunicationBench is our own test: eighty real email and message requests, judged blind. Hemmingway-1 scored 1026, level with Claude's Fable 5.1 at 1024 and ahead of GPT-6 Astra at 976. The full results show where the gaps are.
Those are tests of models. Gemini, Copilot, Grammarly and Superhuman were not in them, so we do not rank those four. We describe what each says it does.
What a good AI email looks like
Whatever you use, check the draft against four things.
- It uses the facts you gave and adds none. A made-up date or reason is the fault to look for.
- It is one email, not three options and a note about tone.
- It is as long as the matter needs, and no longer.
- It sounds like you writing to that person.
Say you are Marta, and the facts you give are these: tell Priya at the print shop that the menus are needed by Thursday, not Friday, because the opening has moved forward a day, and ask if that is possible. An email along these lines is what to expect:
Hi Priya,
Our opening has moved forward a day, so we now need the menus by Thursday rather than Friday. Is that possible at your end?
Thanks,
Marta
Short, nothing invented, ready to send. For the rules behind it, see how to write a professional email.
Where Hemmingway fits, and where it does not
It fits email to people: the reply to a client, the awkward note to a colleague, the message you have put off. It fits if you want replies drafted across mail and chat apps in one list, and if you want the words to sound like yours.
It does not fit everything. It is a separate app, so if you never want to leave Gmail's compose window, Gemini is nearer to hand. It is built around your own voice, not a company's, so marketing email for a brand is a job for a marketing tool. It is English-first. And it can be wrong and still sound certain, so read anything about money, law or health before it goes. Hemmingway writes the email. You send it.
How to choose
- If you never leave Gmail or Outlook, start with the assistant built into it.
- If you write fine but want a second pair of eyes, use a checker.
- If the email never gets started, use a tool that writes from the facts.
- Test on a real email you owe someone. Count the words you change before you would send it.
Try HemmingwayDownload the app
Common questions
What is the best AI email writer?
The one that sits where you write and gives you a draft you would send. In Gmail, start with Gemini. In Outlook, start with Copilot. For a whole email written from a few facts, Hemmingway-1 came first in our own blind test of eighty email and message requests, level with Claude's Fable 5.1.
Is there a free AI email writer?
Yes. Hemmingway's AI email writer opens a free trial with no card needed, with your answers filled in. Grammarly's site says you can start for free, and ChatGPT's site says its free version is open to everyone. Free plans have limits, so check each site.
Can AI reply to my emails for me?
In the Hemmingway apps for Mac, Windows and Android, Inbox drafts each reply and waits for you to send it. Autopilot, in the Mac and Android apps on paid plans, can answer the easy ones by rules you set. It is off until you switch it on.
Is ChatGPT good for writing emails?
It is quick and direct. In our tests GPT-6 Astra's messages were short and rarely came with commentary, but they scored 976 on everyday messages against Hemmingway-1's 1026, and lower on sounding like a person. Both tests are our own benchmarks.