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

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

| | First-choice share | Rank | Negative rate | Labels | Models naming it |
|---|---|---|---|---|---|
| GlockApps | 34% | #1 of 12 | 7% | 57 | 14 of 14 |
| Mail-Tester | 5% | #5 of 12 | 25% | 20 | 11 of 14 |

## The direct prompt, model by model

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

## What the models said about GlockApps

- "GlockApps became popular for one specific capability... Test credits do not roll over... stops at telling you what is wrong." (Muse Glimmer 30B, negative prompt, soft negative)
- "a fraction of what enterprise tools like GlockApps ($85+/month) or ZeroBounce ($99/month) would cost" (DeepSeek V4 Flash, budget prompt, soft negative)
- "Good for deeper testing, but pricier; consider only if you have repeated deliverability issues" (GLM 4.7 FlashX, budget prompt, soft negative)
- "For most mid-sized B2B companies, GlockApps offers the best balance of comprehensive diagnostics, B2B-appropriate seed lists, and reasonable pricing." (Claude Haiku 4.5, paraphrase prompt, first choice)
- "the best choice is usually GlockApps if you want the strongest balance of inbox placement testing, DMARC monitoring, and mid-market pricing" (Perplexity Sonar, direct prompt, first choice)
- "For most mid-sized B2B companies, GlockApps is the best choice due to its depth of inbox placement testing and deliverability diagnostics." (Mistral Small, paraphrase prompt, first choice)

## 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)

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.