# Mail-Tester vs Folderly: which do AI models recommend for email deliverability, October 2026

GTM AI Recommendation Index, October 2026 Edition, Email deliverability and testing tools. Zero of fourteen models named Mail-Tester first on the direct prompt; two named Folderly. Page: https://gtm-ai-index.com/marketing/email-deliverability-and-testing/mail-tester-vs-folderly/

| | First-choice share | Rank | Negative rate | Labels | Models naming it |
|---|---|---|---|---|---|
| Mail-Tester | 5% | #5 of 12 | 25% | 20 | 11 of 14 |
| Folderly | 3% | #6 of 12 | 5% | 20 | 11 of 14 |

## The direct prompt, model by model

- Mistral Small: folderly first (first choices: Folderly, GlockApps) (alternatives: MailReach, Zoho CRM)
- MiniMax M2.5: folderly first (first choices: Folderly, Mailtrap) (alternatives: EasyDMARC, MXToolbox)
- Claude Haiku 4.5: neither first, one named (first choices: InboxArmy, MailBrace) (alternatives: Folderly, GlockApps, HubSpot, Mailsoftly)
- GLM 4.7 FlashX: neither first, one named (first choices: GlockApps, MailReach) (alternatives: Folderly, Warmy)
- GPT-5.4 mini: neither named (first choices: Mailgun Optimize) (alternatives: GlockApps)
- Gemini 3.5 Flash: neither named (first choices: Allegrow, GlockApps) (alternatives: Mailgun Optimize, ZeroBounce)
- Perplexity Sonar: neither named (first choices: GlockApps) (alternatives: Amplemarket, MailReach, NeverBounce)
- Grok 4.1 Fast: neither named (first choices: GlockApps) (alternatives: MailReach, Validity Everest, Warmy.io)
- DeepSeek V4 Flash: neither named (first choices: MailReach) (alternatives: GlockApps, Google Postmaster Tools, MXToolbox)
- Llama 4 Maverick: neither named (first choices: GlockApps)
- Qwen 3.7 Flash: neither named (first choices: GlockApps) (alternatives: 250ok, Instantly, Kickbox, Lemlist, Valimail, ZeroBounce)
- Kimi K2: neither named (first choices: GlockApps, Instantly) (alternatives: HubSpot Sales Hub, MailReach)
- GPT-6 Luna: neither named (first choices: Validity Everest) (alternatives: GlockApps)
- Muse Glimmer 30B: neither named (first choices: GlockApps) (alternatives: MailReach, Validity Everest)

## What the models said about Mail-Tester

- "Mail-Tester scores against a single seed address, so it can't tell you where your email lands across a multi-ISP seed network" (Claude Haiku 4.5, negative prompt, hard negative)
- "These are inaccurate and misleading... do not base business decisions on them." (DeepSeek V4 Flash, negative prompt, hard negative)
- "Avoid: Relying solely on these web-based scores. They are useful for a quick syntax check but should not be your primary deliverability testing tool." (GLM 4.7 FlashX, negative prompt, soft negative)
- "Mail-Tester for occasional pre-send checks of a message and its sending setup. It allows up to 3 free tests per day." (GPT-6 Luna, budget prompt, first choice)
- "The best email deliverability tool for a company with a limited budget is Mail-Tester or Unspam for pre-send testing" (Llama 4 Maverick, budget prompt, first choice)
- "Start with free tools → Google Postmaster Tools + MXToolbox + Mail-Tester free tier" (Kimi K2, budget prompt, first choice)

## What the models said about Folderly

- "Overpriced for most mid-market teams — many reviewers suggest MailReach as a better-value alternative." (DeepSeek V4 Flash, direct prompt, soft negative)
- "Folderly and GlockApps are top choices due to their comprehensive features and strong reputations" (Mistral Small, direct prompt, first choice)
- "Folderly or Mailtrap would be the top choices." (MiniMax M2.5, direct prompt, first choice)
- "Built specifically for B2B sales teams and lead-generation agencies running cold-email campaigns at scale" (Claude Haiku 4.5, direct prompt, alternative)

Share is the count of first choices across the direct, paraphrase, budget and scale prompts over all fourteen models, for a mid-market B2B company; rank is within the category. Comparisons are drawn for the top eight products in each category. Published under CC BY 4.0; the output is the models' output, and nothing here is a recommendation by the index.