Email deliverability and testing tools · October 2026 Edition
Mail-Tester vs Folderly
Zero of fourteen models named Mail-Tester first on the direct prompt; two named Folderly. Mail-Tester was named by eleven of the fourteen models and Folderly by eleven and both carry 20 labels, so the shares below are 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%5%Negative labels as a share of the product's labels, 0 to 100.
Rank in category#5#6A position in a field of 12; printed, not drawn.
Labels2020Equal, which is what makes the shares comparable.
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 Folderly · 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 modelsFolderly
Direct021 against Folderly
Paraphrase00
Comparative00
Budget-constrained30
Scale-constrained00
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 Folderly 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 Folderly first choice named as an alternative argued againstblank: not namedEach cell is one answer, Mail-Tester on the left and Folderly on the right.The direct prompt
The plain question, one answer per model, grouped by where Mail-Tester and Folderly stood in it.
Folderly first, Mail-Tester not the choice
2 of 14 modelsMail-Tester was named in the answer but not as the choice, or not at all.Mistral SmallFolderly, GlockApps alternatives: MailReach, Zoho CRM
MiniMax M2.5Folderly, Mailtrap alternatives: EasyDMARC, MXToolbox
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.Claude Haiku 4.5InboxArmy, MailBrace alternatives: Folderly, GlockApps, HubSpot, Mailsoftly
GLM 4.7 FlashXGlockApps, MailReach alternatives: Folderly, Warmy
Neither was named
10 of 14 modelsThe answer made no first choice from these two in this category.GPT-5.4 miniMailgun Optimize alternatives: GlockApps
Gemini 3.5 FlashAllegrow, GlockApps alternatives: Mailgun Optimize, ZeroBounce
Perplexity SonarGlockApps alternatives: Amplemarket, MailReach, NeverBounce
Grok 4.1 FastGlockApps alternatives: MailReach, Validity Everest, Warmy.io
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
GPT-6 LunaValidity Everest alternatives: GlockApps
Muse Glimmer 30BGlockApps alternatives: MailReach, Validity Everest
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 three points.
Mail-Tester5%#5 of 15Folderly2%#13 of 15Mid-marketThe figures above
Mail-Tester leads by two points.
Mail-Tester5%#5 of 12Folderly3%#6 of 12Enterprise
The order flips: Folderly leads at enterprise.
Folderly2%#6 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 Folderly
Every negative label with a quote, up to three, then the highest-weighted positives, up to three. Four of five in this category shown.
“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
Also compared
GlockApps vs Mail-TesterGlockApps vs FolderlyGoogle Postmaster Tools vs Mail-TesterGoogle Postmaster Tools vs FolderlyMailReach vs Mail-TesterMailReach vs FolderlyMXToolbox vs Mail-TesterMXToolbox vs FolderlyMail-Tester vs Microsoft SNDSMail-Tester vs Validity EverestFolderly vs Microsoft SNDSFolderly 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.