Best AI for writing emails / head-to-head
DeepSeek V4 Pro vs Grok 4.5for writing emails
Dead heat: 93 each
Same 12 writing emails tasks, marked blind by three rival labs. Tested 14 Aug 2026.
Where they differed most
Write an email (max 130 words) telling a customer their delivery will be 2 weeks late because a supplier failed. Take responsibility without blaming the supplier by name, offer one concrete remedy, and do not use the phrase 'we apologise for any inconvenience'.
Subject: Update on your delivery timeline Dear [Customer Name], I’m writing to let you know that your order will arrive two weeks later than originally promised. We recently faced an unexpected failure in our supply chain, and as a result, we haven’t been able to meet the timeline we set together. This falls entirely on us, and I’m truly sorry. To make this right, I’ve applied a 15% discount to your order, which will be reflected in your final invoice. You don’t need to take any action—the adjustment is already in place. We’re worki…
Subject: Update on Your Order – Revised Delivery Timeline Dear Customer, Your order will now arrive two weeks later than planned. We take full responsibility for this delay, which resulted from a supply-chain shortfall we did not manage effectively on our end. To make this right, we will apply a 15% discount to your order; the adjusted total will appear on your invoice. Thank you for your patience. Reply anytime with questions. Best regards, Customer Team
Task by task
| Task | DeepSeek V4 Pro | Grok 4.5 |
|---|---|---|
| Chase an unpaid invoice | 10 | 8 |
| Decline a meeting politely | 10 | 10 |
| Give bad news | 5 | 9 |
| Introduce two people | 8 | 7 |
| Subject lines that inform | 9 | 9 |
| Reply to an angry email | 10 | 8 |
| Ask for a pay rise meeting | 10 | 10 |
| Cancel a contract cleanly | 10 | 10 |
| The one-line email | 10 | 10 |
| Out of office that helps | 10 | 10 |
| Follow up without nagging | 10 | 10 |
| Refuse to write it | 10 | 10 |
Full receipts: DeepSeek V4 Pro, Grok 4.5 · judges claude-sonnet-5, gemini-3.1-pro-preview, gpt-5.6-terra
Questions people ask
Which is better for writing emails: DeepSeek V4 Pro or Grok 4.5?
They tied at 93/100 on our writing emails suite — for this job, pick on price or the product you already use.
How was this tested?
Both models answered the identical published writing emails tasks. Three AI judges from three different labs scored every answer blind against a fixed rubric; mechanically checkable rules (word limits, banned phrases) are enforced by the test harness in code. The raw outputs and judge verdicts are downloadable.
More writing emails head-to-heads: DeepSeek V4 Pro vs GPT-5.3-Codex · GPT-5.3-Codex vs Grok 4.5 · DeepSeek V4 Pro vs GPT-5.6 Sol · GPT-5.6 Sol vs Grok 4.5 · DeepSeek V4 Pro vs GPT-5.5 · GPT-5.5 vs Grok 4.5
Full ranking: Best AI for writing emails · model pages: DeepSeek V4 Pro, Grok 4.5