The best AI for email writing is the one built into the inbox you already use: Gemini in Gmail and Copilot in Outlook can draft replies directly from the thread. For more control over tone, ChatGPT or Claude write better first drafts when you paste the context, and Grammarly is the best tool for polishing emails you write yourself.
AI email tools compared
| Tool | Works in | Best for | Cost |
|---|---|---|---|
| Gemini in Gmail | Gmail | Replies from the thread, summaries | Paid Google AI or Workspace plans |
| Copilot in Outlook | Outlook | Drafts, thread summaries, tone coaching | Microsoft 365 Copilot |
| ChatGPT | Any, by copy and paste | Tricky messages, many variations | Free tier, Plus $20/month (US) |
| Claude | Any, by copy and paste | Natural tone, long context | Free tier, Pro $20/month (US) |
| Grammarly | Browser, Gmail, Outlook | Grammar, clarity, tone checks | Free and paid |
When built-in assistants are best
Gemini and Copilot read the whole thread, so they know who said what and what is being asked. That makes them fast for everyday replies, scheduling and summarizing long chains. They also keep the email inside your company’s approved tools.
When a general chatbot is better
For a difficult message, such as declining a client, chasing a late payment or giving feedback, a general assistant gives you more control. You can explain the background, ask for three tones, and iterate. Claude tends to produce warmer, less templated phrasing; ChatGPT is quick at variations. See Claude vs ChatGPT.
Prompts for common emails
- “Reply to this email. Accept the meeting, suggest Thursday instead of Tuesday, keep it to three sentences: [email]”
- “Write a polite follow-up to a client who has not paid invoice [number], due [date]. Firm but friendly, no threats.”
- “Decline this partnership offer without closing the door for the future: [email]”
- “Summarize this thread in five bullet points and tell me what I need to answer: [thread]”
- “Rewrite my draft so it is shorter and clearer. Keep my wording where possible: [draft]”
- “Write a cold email to [role] at [type of company] about [offer]. Under 100 words, one clear question at the end.”
More templates are in our ChatGPT prompts collection.
How to keep emails sounding like you
Paste three emails you have written and ask the AI to describe your style, then add “write in this style” to future prompts. Ask for short sentences and no filler phrases. Always rewrite the first line and the sign-off yourself; those are where generic AI phrasing is most noticeable.
Privacy and accuracy
Do not paste confidential contracts, passwords or personal data into a personal AI account. Check names, dates, numbers and commitments in every draft before sending, because AI can misread a thread or invent details. And never let an assistant send emails automatically on your behalf without reviewing them.
For longer writing tasks, see the best AI for writing. For team-wide use of AI in email and documents, read ChatGPT for business.
Frequently asked questions
Can AI write emails in Gmail?
Yes. Gemini is built into Gmail on paid Google plans and can draft replies from the thread. Gmail's Smart Compose also suggests text as you type, and Grammarly works in Gmail through a browser extension.
Is it safe to use AI for work emails?
Use the assistant your company approves. Business plans of Google, Microsoft, OpenAI and Anthropic exclude your data from model training by default; personal free accounts may not.
How do I make AI emails sound less robotic?
Give the AI a few of your past emails as examples, ask for short sentences and plain words, and edit the opening and closing yourself.