# Email deliverability and testing tools: what AI models recommend, November 2026

Gane Index, November 2026 Edition. Asked as "email deliverability tool" and as "inbox placement and email testing platform", six framings each, to fourteen models with search on, on behalf of a mid-market B2B company. Added to the November 2026 Edition. Page: https://www.gane.ai/index/gtm/marketing/email-deliverability-and-testing

**Standing:** GlockApps leads with 38% of first choices; verdict contested. 50 first choices across the direct, paraphrase, budget and scale prompts.

## First-choice share

| Rank | Product | Share | Negative rate | Labels |
|---|---|---|---|---|
| 1 | [GlockApps](https://www.gane.ai/index/gtm/vendors/glockapps/index.md) | 38% | 9% | 57 |
| 2 | [Google Postmaster Tools](https://www.gane.ai/index/gtm/vendors/google-postmaster-tools/index.md) | 10% | 6% | 34 |
| 4 | [Litmus](https://www.gane.ai/index/gtm/vendors/litmus/index.md) | 6% | 10% | 21 |
| 5 | [ZeroBounce](https://www.gane.ai/index/gtm/vendors/zerobounce/index.md) | 4% | 14% | 28 |
| 8 | [MXToolbox](https://www.gane.ai/index/gtm/vendors/mxtoolbox/index.md) | 2% | 6% | 32 |
| 9 | [MailReach](https://www.gane.ai/index/gtm/vendors/mailreach/index.md) | 2% | 8% | 25 |
| 10 | [Validity Everest](https://www.gane.ai/index/gtm/vendors/validity-everest/index.md) | 2% | 22% | 32 |
| 11 | [Mail-Tester](https://www.gane.ai/index/gtm/vendors/mail-tester/index.md) | 2% | 19% | 27 |
| 12 | [Folderly](https://www.gane.ai/index/gtm/vendors/folderly/index.md) | 2% | 14% | 14 |
| 14 | [Mailgun](https://www.gane.ai/index/gtm/vendors/mailgun/index.md) | 2% | 10% | 10 |
| 20 | [Microsoft SNDS](https://www.gane.ai/index/gtm/vendors/microsoft-snds/index.md) | 0% | 0% | 17 |
| 21 | [Mailtrap Email Sandbox](https://www.gane.ai/index/gtm/vendors/mailtrap-email-sandbox/index.md) | 0% | 13% | 15 |

Rank is by share of first choices among all 124 products named; products with the same share are tied, and the order among them carries no meaning. The table lists those with at least 10 labels.

## Each model's first choice on the direct prompt

- Claude Haiku 4.5: Warmy; alternatives Act-On, GlockApps, MailReach, Mailtrap Email Marketing
- GPT-5.4 mini: Litmus; alternatives Brevo, HubSpot, Salesforce/Marketing Cloud, ZeroBounce
- Gemini 3.5 Flash: GlockApps; alternatives Folderly, Google Postmaster Tools, Mailgun Optimize, Mailtrap Email Sandbox
- Perplexity Sonar: GlockApps; alternatives EasyDMARC, Google Postmaster Tools, MailReach, Microsoft SNDS
- Grok 4.20: GlockApps; alternatives Allegrow, Validity Everest
- Mistral Small: Allegrow, Validity Everest; alternatives Litmus
- DeepSeek V4 Flash: HubSpot Sales Hub; alternatives GlockApps, Klaviyo, Lemlist, Mailgun
- Llama 4 Maverick: GlockApps; alternatives MailReach, Validity Everest
- Qwen 3.7 Flash: GlockApps, ZeroBounce; alternatives Kickbox, NeverBounce, Red Sift OnDMARC, SendForensics
- Kimi K2: Allegrow; alternatives GlockApps, MailReach
- GLM 4.7 FlashX: GlockApps; alternatives Allegrow, MailReach
- MiniMax M2.5: HubSpot Sales Hub, ZeroBounce; alternatives Copper, GlockApps, MXToolbox
- GPT-6 Luna: GlockApps; alternatives Google Postmaster Tools, Validity Engage
- Muse Glimmer 30B: GlockApps, MailGenius; alternatives Allegrow, Amplemarket

## Sources the answers cite

72 of 84 answers came back with a source list, from 14 of 14 models. Sites named in the most answers:

- unspam.email: 24 answers, 27 citations
- glockapps.com: 23 answers, 44 citations
- salesdorado.com: 19 answers, 19 citations
- mailtrap.io: 16 answers, 17 citations
- g2.com: 15 answers, 20 citations
- emailtooltester.com: 15 answers, 17 citations
- myemailverifier.com: 15 answers, 15 citations
- mailtester.com: 14 answers, 51 citations

Pages named in the most answers:

- https://myemailverifier.com/blog/email-deliverability-tools (15 answers)
- https://glockapps.com/ (14 answers)
- https://sendlayer.com/blog/best-email-deliverability-tools (14 answers)
- https://unspam.email/articles/email-deliverability-softwares (14 answers)
- https://omnisend.com/blog/email-deliverability-tools (11 answers)
- https://softwaresuggest.com/email-deliverability-tools (11 answers)
- https://salesdorado.com/en/inbound-marketing/email-testing-tools (10 answers)
- https://amplemarket.com/blog/best-email-deliverability-tools (9 answers)
- https://rajeshkumar.xyz/blog/email-deliverability-tools (9 answers)
- https://saasworthy.com/list/email-deliverability?page=2 (9 answers)

## Warned against

- Validity Everest: 7 of 32 labels negative. "Unnecessary enterprise tools (Validity Everest, etc.) unless you're at scale." (GLM 4.7 FlashX, budget prompt)
- GlockApps: 5 of 57 labels negative. "Seed-list placement testers such as GlockApps, Unspam, or similar tools: useful for directional comparisons, but test accounts do not behave like real subscribers" (Perplexity Sonar, negative prompt)
- Mail-Tester: 5 of 27 labels negative. "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)
- ZeroBounce: 4 of 28 labels negative. "Address-verification services such as ZeroBounce, Kickbox, or comparable vendors: treat results as risk estimates, not proof of consent" (Perplexity Sonar, negative prompt)

## Movement since October 2026

Floor: 11 points of share, measured on the calibration repeat.
Same leader: GlockApps at 38%.

- Litmus: 0% to 6%, +6. Inside the floor by 5 points · rank 26 → 4 of 124.
- MailReach: 7% to 2%, −5. Inside the floor by 6 points · rank 3 → 9 of 124.
- GlockApps: 34% to 38%, +4. Inside the floor by 7 points · rank 1 of 124, unchanged.
- ZeroBounce: 0% to 4%, +4. Inside the floor by 7 points · rank 27 → 5 of 124.
- MXToolbox: 5% to 2%, −3. Inside the floor by 8 points · rank 4 → 8 of 124.
- Mail-Tester: 5% to 2%, −3. Inside the floor by 8 points · rank 5 → 11 of 124.
- Microsoft SNDS: 3% to 0%, −3. Inside the floor by 8 points · rank 7 → 20 of 124.
- Mailgun: 0% to 2%, +2. Inside the floor by 9 points · rank 28 → 14 of 124.
- Mailtrap Email Sandbox: 2% to 0%, −2. Inside the floor by 9 points · rank 10 → 21 of 124.
- Warmup Inbox: 2% to 0%, −2. Inside the floor by 9 points · rank 24 → 26 of 124.
- Instantly: 2% to 0%, −2. Inside the floor by 9 points · rank 14 → 39 of 124.
- Google Postmaster Tools: 9% to 10%, +1. Inside the floor by 10 points · rank 2 of 124, unchanged.

## Record

- Method: https://www.gane.ai/index/gtm/methodology
- License: CC BY 4.0. Cite as Gane Index, November 2026 Edition, www.gane.ai/index/gtm.