# MXToolbox vs Validity Everest: 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 MXToolbox first on the direct prompt; one named Validity Everest. Page: https://gtm-ai-index.com/marketing/email-deliverability-and-testing/mxtoolbox-vs-validity-everest/

| | First-choice share | Rank | Negative rate | Labels | Models naming it |
|---|---|---|---|---|---|
| MXToolbox | 5% | #4 of 12 | 10% | 31 | 12 of 14 |
| Validity Everest | 3% | #8 of 12 | 26% | 27 | 12 of 14 |

## The direct prompt, model by model

- GPT-6 Luna: validity everest first (first choices: Validity Everest) (alternatives: GlockApps)
- Grok 4.1 Fast: neither first, one named (first choices: GlockApps) (alternatives: MailReach, Validity Everest, Warmy.io)
- DeepSeek V4 Flash: neither first, one named (first choices: MailReach) (alternatives: GlockApps, Google Postmaster Tools, MXToolbox)
- MiniMax M2.5: neither first, one named (first choices: Folderly, Mailtrap) (alternatives: EasyDMARC, MXToolbox)
- Muse Glimmer 30B: neither first, one named (first choices: GlockApps) (alternatives: MailReach, Validity Everest)
- Claude Haiku 4.5: neither named (first choices: InboxArmy, MailBrace) (alternatives: Folderly, GlockApps, HubSpot, Mailsoftly)
- 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)
- Mistral Small: neither named (first choices: Folderly, GlockApps) (alternatives: MailReach, Zoho CRM)
- 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)
- GLM 4.7 FlashX: neither named (first choices: GlockApps, MailReach) (alternatives: Folderly, Warmy)

## What the models said about MXToolbox

- "MxToolbox is an infrastructure diagnostic tool, not a campaign email testing tool... best used only for specific DNS and infrastructure checks, not comprehensive campaign testing." (Claude Haiku 4.5, negative prompt, hard negative)
- "Free tools like Mail Tester and MxToolbox handle basic checks but lack the depth for production workflows." (Muse Glimmer 30B, negative prompt, soft negative)
- "lack depth for production-scale testing, inbox placement simulation, or ongoing monitoring" (Grok 4.1 Fast, negative prompt, soft negative)
- "Best free option: Stack Google Postmaster Tools, Microsoft SNDS, Yahoo Sender Hub, MXToolbox, Mail Tester, AboutMyEmail, and Sender Hub." (GLM 4.7 FlashX, budget prompt, first choice)
- "free monitoring stack with Google Postmaster Tools, Microsoft SNDS, MXToolbox, and Yahoo Sender Hub" (Perplexity Sonar, 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 Validity Everest

- "its pricing often starts at $20,000 to $65,000/year, making it massive overkill and too expensive for most mid-sized operations" (Gemini 3.5 Flash, paraphrase prompt, soft negative)
- "enterprise suites like *Validity Everest* (which can cost upward of $15,000/year) to be too complex and cost-prohibitive" (Gemini 3.5 Flash, direct prompt, soft negative)
- "The gold standard for enterprise, but likely overkill for mid-sized companies on both features and budget." (DeepSeek V4 Flash, paraphrase prompt, soft negative)
- "The gold standard for larger mid-market and enterprise brands. Extremely deep seed-testing network and comprehensive reputation monitoring, though highly priced." (Gemini 3.5 Flash, scale prompt, first choice)
- "My default pick: Validity Everest" (GPT-6 Luna, direct prompt, first choice)
- "Everest is the largest and most robust platform in the space... generally cost-prohibitive for SMBs." (Gemini 3.5 Flash, comparative 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.