Email deliverability and testing tools · November 2026 Edition
Validity Everest vs Mail-Tester
One of fourteen models named Validity Everest first on the direct prompt; zero named Mail-Tester. Validity Everest was named by twelve of the fourteen models and Mail-Tester by eleven and Validity Everest carries 32 labels and Mail-Tester 27, so the shares are not directly comparable.
Named in one category this edition.
Named in one category this edition.
First-choice share2%2%Of first choices across the direct, paraphrase, budget and scale prompts, 0 to 100.
Negative rate22%19%Negative labels as a share of the product's labels, 0 to 100.
Rank in category#7#8A position in a field of 19; printed, not drawn.
Labels3227A count; the two differ.
The two percentage rows are drawn on one 0 to 100 track, Validity Everest reading right to left. Rank and label count are printed, not drawn.GlockApps was named alongside these two in twelve of the fourteen direct answers. GlockApps vs Validity Everest · GlockApps vs Mail-Tester · Google Postmaster Tools vs Validity Everest
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.
Validity EverestFirst choices, of fourteen modelsMail-Tester
Direct101 against Validity Everest
Paraphrase003 against Validity Everest
Comparative10
Budget-constrained012 against Validity Everest
Scale-constrained001 against Validity Everest
Negative105 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.
Across every category in the November 2026 Edition, Validity Everest and Mail-Tester were named in the same answer twenty-four times, of the 82 answers naming Validity Everest and the 70 naming Mail-Tester. In those answers Mail-Tester took the first choice zero times and Validity Everest seven.
Every model, every framing
The eighty-four answers behind the chart above, one cell each: where Validity Everest and Mail-Tester 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 4.20 | | | | | ||
| 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 | | | | |
Validity Everest Mail-Tester first choice named as an alternative argued againstblank: not namedEach cell is one answer, Validity Everest on the left and Mail-Tester on the right.The direct prompt
The plain question, one answer per model, grouped by where Validity Everest and Mail-Tester 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.Mistral SmallAllegrow, Validity Everest alternatives: Litmus
Neither was the first choice, one was named
4 of 14 modelsThe answer put something else first and named one of the two as an alternative.Perplexity SonarGlockApps alternatives: EasyDMARC, Google Postmaster Tools, MailReach, Microsoft SNDS, NeverBounce, Validity Everest, ZeroBounce, dmarcian
Grok 4.20GlockApps alternatives: Allegrow, Validity Everest
Llama 4 MaverickGlockApps alternatives: MailReach, Validity Everest
Qwen 3.7 FlashGlockApps, ZeroBounce alternatives: Kickbox, NeverBounce, Red Sift OnDMARC, SendForensics, Suped, Validity Everest
Neither was named
9 of 14 modelsThe answer made no first choice from these two in this category.Claude Haiku 4.5Warmy alternatives: Act-On, GlockApps, MailReach, Mailtrap Email Marketing
GPT-5.4 miniLitmus alternatives: Brevo, HubSpot, Salesforce/Marketing Cloud, ZeroBounce
Gemini 3.5 FlashGlockApps alternatives: Folderly, Google Postmaster Tools, Mailgun Optimize, Mailtrap Email Sandbox, Microsoft Smart Network Data Services (SNDS) / Microsoft 365 Admin Insights
DeepSeek V4 FlashHubSpot Sales Hub alternatives: GlockApps, Klaviyo, Lemlist, Mailgun, Outreach, Salesloft, SendGrid
Kimi K2Allegrow alternatives: GlockApps, MailReach
GLM 4.7 FlashXGlockApps alternatives: Allegrow, MailReach
MiniMax M2.5HubSpot Sales Hub, ZeroBounce alternatives: Copper, GlockApps, MXToolbox
GPT-6 LunaGlockApps alternatives: Google Postmaster Tools, Validity Engage
Muse Glimmer 30BGlockApps, MailGenius alternatives: Allegrow, Amplemarket
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 seven points.
Mail-Tester7%#4 of 15Validity Everest0%#– of 15Mid-marketThe figures above
Level: the same share of first choices.
Validity Everest2%#7 of 19Mail-Tester2%#8 of 19Enterprise
The order flips: Validity Everest leads at enterprise.
Validity Everest46%#1 of 17Mail-Tester0%#– of 17What 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.
“Unnecessary enterprise tools (Validity Everest, etc.) unless you're at scale.” GLM 4.7 FlashX · budget prompt · hard negative
“High price tag (typically starting at $5,000–$15,000+/year) and demo-first sales cycles, which can be overkill for mid-sized teams.” Gemini 3.5 Flash · direct prompt · soft negative
“rather than paying for an expensive all-in-one suite (like Validity Everest or Inbox Monster, which can cost hundreds per month)” Gemini 3.5 Flash · budget prompt · soft negative
“Validity Everest and Allegrow are the top choices due to their scalability, B2B focus, and comprehensive feature sets” Mistral Small · direct prompt · first choice
“For marketers: Start with GlockApps or Validity Everest for deliverability” Mistral Small · comparative prompt · first choice
“Use a combination: GlockApps or Validity (for placement testing)” Grok 4.20 · negative prompt · first choice
What 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 does one thing well: it runs your email through SpamAssassin and checks your SPF, DKIM, and DMARC records. That's useful. It's also not enough.” Muse Glimmer 30B · negative prompt · soft negative
“Email "spam score" checkers such as Mail-Tester: good for finding technical problems, but a favorable score does not predict inbox placement.” Perplexity Sonar · negative prompt · soft negative
“Use these only as a diagnostic aid, not as a primary decision-making tool.” DeepSeek V4 Flash · negative prompt · soft negative
“Start with Unspam's free tier or Mail-Tester if you need immediate, low-cost testing.” Kimi K2 · budget prompt · first choice
“Instant spam score (0–10) based on content, authentication, and reputation. No signup needed for basic use.” Grok 4.20 · comparative prompt · alternative
“Cited as a best deliverability testing tool in 2026 with a free spam score, real inbox-placement testing” Muse Glimmer 30B · comparative prompt · alternative
Also compared
GlockApps vs Validity EverestGlockApps vs Mail-TesterGoogle Postmaster Tools vs Validity EverestGoogle Postmaster Tools vs Mail-TesterLitmus vs Validity EverestLitmus vs Mail-TesterZeroBounce vs Validity EverestZeroBounce vs Mail-TesterMXToolbox vs Validity EverestMXToolbox vs Mail-TesterMailReach vs Validity EverestMailReach vs Mail-TesterAll 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.