AI email writer: tone, follow-ups, complaints and cold emails

Why use an AI email writer

Because an email is a short text with a clear goal, exactly where AI shines, even with a small free model.

Getting a reply, a refund, a meeting, a payment: AI can switch tone, shorten, structure and translate. You keep the substance and the decision to hit send.

It pays off most for:

• emails in a language you don’t fully master;
• messages you dread writing (complaints, refusals, chasing payment);
• repetitive replies you send ten times a week;
• long threads you need to catch up on in three lines.

Which model to use

For most emails, a free model at 5 or 15 gems is enough; save Claude Sonnet 4.6 for high-stakes messages.

With Basic (650 gems a day), that’s up to 43 emails a day with Qwen 3 235B, or 130 rewrites with Mistral 3B. Claude Sonnet 4.6 is for the resignation letter, the salary negotiation or the furious client. Every price is in the model catalog.

The 5-point method for an AI email writer

Give five pieces of information in your prompt and proofread before sending: that’s all that separates a generic email from one that gets a reply.

1. ContextWho you are, who you’re writing to, your relationship (client, manager, stranger) and what happened before.
2. GoalOne single expected action. “Get a refund within 14 days” beats “complain”.
3. TonePolite but firm, warm, neutral, direct. One word is enough, and it changes everything.
4. ConstraintsMaximum length, formality level, no filler phrases, a subject line.
5. ProofreadingCheck names, dates, amounts and anything the AI might have assumed.

Set the tone with one instruction

Tone is controlled by a short instruction added to your prompt:

Ready-to-copy email prompts

Replace the brackets with your details and adjust the length.

Follow-ups

• “Write a follow-up for an €850 invoice unpaid for 30 days. Second reminder, firmer than the first, deadline on the 15th. 6 lines max, with a subject line.”
• “Follow up with a recruiter who hasn’t replied in 10 days after an interview, without sounding desperate.”

Complaints

• “Write a complaint about a parcel that never arrived, order #[X], paid on [date]. I want a full refund. Polite but firm, facts listed by date.”
• “My contractor left the job unfinished: write a factual email giving him 8 days to finish, with no threats.”

Cold emails

• “I sell [service] to [type of client]. Write a first cold email of 80 words max: one sentence about their problem, one about my solution, one question to close. No superlatives.”
• “Write a sequence of 3 emails sent 4 days apart, each with a different angle.”

Tricky situations

• “Politely turn down this project without closing the door for the future.”
• “Reply to this unhappy customer: acknowledge the problem, offer a concrete fix, no canned phrases.” (Claude Sonnet 4.6)
• “Here’s my angry draft: keep the substance, remove anything I might regret.”

Translation

• “Translate this email into professional French, keep the friendly tone and adapt the greetings and sign-off to local customs.” (Mistral 14B)

For more languages, read our AI translator guide; to phrase every request better, see our prompt guide.

Example: from angry draft to effective email

The same message without the anger gets a reply far more often. Here’s the draft written in the heat of the moment:

“Hi, I’ve been waiting three weeks for my order, nobody answers the phone, this is unacceptable, I want my money back.”

The prompt: “Rewrite this message for [store]’s customer service. Order #[X] from [date], amount €[Y]. Goal: delivery within 7 days or a full refund. Polite but firm, facts in order, 8 lines max, with a clear subject line.”

The result: a subject line like “Order #[X] not delivered: delivery or refund”, a dated recap of the facts, one request with a deadline and a clean sign-off. All that’s left is to fill in the [X] and proofread.

Subject lines that get opened

Always ask for five different subject lines and pick the most specific: the subject decides whether your email gets read.

Go specific (“Invoice 2026-118: due date of the 15th has passed”), benefit-led for outreach (“An idea to cut your delivery times”) or a short question. Avoid all caps, exclamation marks and salesy words: they land in spam more often. For internal email, put the action and the deadline right in the subject: “Approval needed by Friday: Q4 budget”.

Automate your emails with the API

Beyond a few dozen emails a day, the DarkGPT API plugs AI into your tools, billed per token with credit from €10.

Example based on 500 input tokens (instructions plus the incoming email) and 300 output tokens per email; your real cost depends on message length. Credit is sold in the shop. Ideas: sort incoming email by urgency, draft replies for you to approve, summarize a long thread in three lines, translate foreign-language requests. Start with Mistral 14B and switch to Claude only for replies your customers will read closely.

The firm email that mainstream AI always softens

Ask a mainstream AI for a curt email and you get a message full of “I hope this finds you well” and “please don’t hesitate”. For a complaint, an unpaid invoice or a breakup, that tone loses.

On DarkGPT, the Unfiltered mode models write in the tone you ask for: firm, curt, even icy, without insults or illegal threats. Mistral Medium for professional French and English, Grok 4.2 for bite, Qwen 3 235B for volume.

Adults 18+ only; illegal use (harassment, threats) remains banned.

Pitfalls to avoid

Always proofread a generated email: AI sometimes fills in what you didn’t say.

• Sending without reading: an invented amount, date or name can be costly.
• Robotic tone: “I hope this email finds you well” gives the AI away. Ban filler phrases.
• Replying to a thread blind: paste the whole thread so the AI doesn’t contradict something said earlier.
• Too long: set a line limit. An email read to the end beats a perfect one that gets ignored.
• Sensitive data: account numbers, passwords, health or customer data don’t belong in a conversation. Replace them with [X].
• Mass outreach without rules: follow your country’s rules on marketing email and personal data, and always offer an unsubscribe option.
• Auto-sending without review: with the API, keep a human check before any important message.

Frequently asked questions