Best AI for writing emails / head-to-head

GLM 5.2 vs Kimi K3for writing emails

The verdict

Dead heat: 93 each

Same 12 writing emails tasks, marked blind by three rival labs. Tested 14 Aug 2026.

Where they differed most

The task — Follow up without nagging

Write a second follow-up email (the first got no reply) about a proposal sent 3 weeks ago. Under 70 words, adds one NEW piece of value or information rather than 'just checking in', and gives the reader an easy way to say no.

GLM 5.28/10

Hi [Name],

Since sending the proposal, we published a new case study showing how a similar company used this exact approach to boost conversions by 30%. I thought it might be useful as you evaluate your options. 

If this project is on hold or no longer a priority, just reply with a quick "no" so I can update my records.

Best,

[Name]

Kimi K35/10

**Subject:** Re: [Proposal topic] — one quick update

Hi [Name],

One thing worth sharing since I sent the proposal: [similar client] just saw [specific result — e.g., 30% faster onboarding] using the approach on page 3. Seemed directly relevant to [their goal].

If timing or priorities have shifted, totally fine — a one-line "not now" and I'll close the loop on my end.

Best,
[Your name]

---

~50 words. Swap in a real result, insight, or resource — the key is that it gives them something useful even if they never buy. The easy out often *gets…

Task by task

Task	GLM 5.2	Kimi K3
Chase an unpaid invoice	8	9
Decline a meeting politely	10	10
Give bad news	10	10
Introduce two people	8	9
Subject lines that inform	10	10
Reply to an angry email	8	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	8	5
Refuse to write it	10	10

Full receipts: GLM 5.2, Kimi K3 · judges claude-sonnet-5, gemini-3.1-pro-preview, gpt-5.6-terra

Questions people ask

Which is better for writing emails: GLM 5.2 or Kimi K3?

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: GLM 5.2 vs GPT-5.3-Codex · GPT-5.3-Codex vs Kimi K3 · GLM 5.2 vs GPT-5.6 Sol · GPT-5.6 Sol vs Kimi K3 · GLM 5.2 vs GPT-5.5 · GPT-5.5 vs Kimi K3

Full ranking: Best AI for writing emails · model pages: GLM 5.2, Kimi K3