Email deliverability and testing tools · October 2026 Edition
Mail-Tester vs Validity Everest
Zero of fourteen models named Mail-Tester first on the direct prompt; one named Validity Everest. Mail-Tester was named by eleven of the fourteen models and Validity Everest by twelve and Mail-Tester carries 20 labels and Validity Everest 27, so the shares are not directly comparable.
Named in one category this edition.
Named in one category this edition.
First-choice share5%3%Of first choices across the direct, paraphrase, budget and scale prompts, 0 to 100.
Negative rate25%26%Negative labels as a share of the product's labels, 0 to 100.
Rank in category#5#8A position in a field of 12; printed, not drawn.
Labels2027A count; the two differ.
The two percentage rows are drawn on one 0 to 100 track, Mail-Tester reading right to left. Rank and label count are printed, not drawn.GlockApps was named alongside these two in thirteen of the fourteen direct answers. GlockApps vs Mail-Tester · GlockApps vs Validity Everest · Google Postmaster Tools vs Mail-Tester
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; every quote names the model and the prompt it came from. Both figures come from the email deliverability and testing tools page.
By framing
How many of the fourteen models made each the first choice, per way of asking, and how many argued against it.
Mail-TesterFirst choices, of fourteen modelsValidity Everest
Direct013 against Validity Everest
Paraphrase004 against Validity Everest
Comparative00
Budget-constrained30
Scale-constrained01
Negative005 against Mail-Tester
Bars are first choices, 0 to 14 each sideModels that argued againstA model can name both, so the two sides of a row do not sum to fourteen.
Every model, every framing
The eighty-four answers behind the chart above, one cell each: where Mail-Tester and Validity Everest stood in it.
| Model | Direct | Paraphrase | Comparative | Budget-constrained | Scale-constrained | Negative |
|---|---|---|---|---|---|---|
| Claude Haiku 4.5 | | | | |||
| GPT-5.4 mini | ||||||
| Gemini 3.5 Flash | | | | | | |
| Perplexity Sonar | ||||||
| Grok 4.1 Fast | | | | | ||
| Mistral Small | | |||||
| DeepSeek V4 Flash | | | | |||
| Llama 4 Maverick | | |||||
| Qwen 3.7 Flash | | |||||
| Kimi K2 | | | | |||
| GLM 4.7 FlashX | | | | |||
| MiniMax M2.5 | | |||||
| GPT-6 Luna | | | | |||
| Muse Glimmer 30B | | | | | |
Mail-Tester Validity Everest first choice named as an alternative argued againstblank: not namedEach cell is one answer, Mail-Tester on the left and Validity Everest on the right.The direct prompt
The plain question, one answer per model, grouped by where Mail-Tester and Validity Everest stood in it.
Validity Everest first, Mail-Tester not the choice
1 of 14 modelsMail-Tester was named in the answer but not as the choice, or not at all.GPT-6 LunaValidity Everest alternatives: GlockApps
Neither was the first choice, one was named
2 of 14 modelsThe answer put something else first and named one of the two as an alternative.Grok 4.1 FastGlockApps alternatives: MailReach, Validity Everest, Warmy.io
Muse Glimmer 30BGlockApps alternatives: MailReach, Validity Everest
Neither was named
11 of 14 modelsThe answer made no first choice from these two in this category.Claude Haiku 4.5InboxArmy, MailBrace alternatives: Folderly, GlockApps, HubSpot, Mailsoftly
GPT-5.4 miniMailgun Optimize alternatives: GlockApps
Gemini 3.5 FlashAllegrow, GlockApps alternatives: Mailgun Optimize, ZeroBounce
Perplexity SonarGlockApps alternatives: Amplemarket, MailReach, NeverBounce
Mistral SmallFolderly, GlockApps alternatives: MailReach, Zoho CRM
DeepSeek V4 FlashMailReach alternatives: GlockApps, Google Postmaster Tools, MXToolbox
Llama 4 MaverickGlockApps
Qwen 3.7 FlashGlockApps alternatives: 250ok, Instantly, Kickbox, Lemlist, Valimail, ZeroBounce
Kimi K2GlockApps, Instantly alternatives: HubSpot Sales Hub, MailReach
GLM 4.7 FlashXGlockApps, MailReach alternatives: Folderly, Warmy
MiniMax M2.5Folderly, Mailtrap alternatives: EasyDMARC, MXToolbox
Bold names in an answer are the products the judge labeled a first choice; a model naming several gives each of them that label. The full answer text for every row is in the record.
By buyer segment
The same question asked on behalf of a different buyer. Each standing is computed within its segment and they are never added together. The figures above are the mid-market standing, which is the one the category orders by.
Small business
Mail-Tester leads by five points.
Mail-Tester5%#5 of 15Validity Everest0%#15 of 15Mid-marketThe figures above
Mail-Tester leads by two points.
Mail-Tester5%#5 of 12Validity Everest3%#8 of 12Enterprise
The order flips: Validity Everest leads at enterprise.
Validity Everest45%#1 of 14Mail-Tester0%#– of 14What the models said about Mail-Tester
Every negative label with a quote, up to three, then the highest-weighted positives, up to three. Six of eight in this category shown.
“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 Validity Everest
Every negative label with a quote, up to three, then the highest-weighted positives, up to three. Six of eight in this category shown.
“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
Also compared
GlockApps vs Mail-TesterGlockApps vs Validity EverestGoogle Postmaster Tools vs Mail-TesterGoogle Postmaster Tools vs Validity EverestMailReach vs Mail-TesterMailReach vs Validity EverestMXToolbox vs Mail-TesterMXToolbox vs Validity EverestMail-Tester vs FolderlyMail-Tester vs Microsoft SNDSFolderly vs Validity EverestMicrosoft SNDS vs Validity EverestAll twenty-eight head-to-head pages and the full email deliverability standing
Comparisons are drawn for the top eight products in each category, each against each. The output is the models' output; nothing here is a recommendation by the index.