These are the three tools most cold-email teams compare us against. Here's a direct, un-padded comparison on what actually matters.
Summary
- Inbox Check: free, 4,000+ seeds, 30+ providers, folder detection, API, MCP/A2A, post-send tracking, domain monitoring, presend analyzer.
- GlockApps: $59–$399/mo, ~100 seeds, broad provider coverage, solid UI, no folder detail on Gmail categories, no MCP.
- MXToolbox: $129–$599/mo, focuses on DNS/auth/blacklists more than placement; limited seed network.
- Mail-Tester: free + paid, small single-seed-per-provider model, famous “/10” score, no agent support.
| Dimension | Inbox Check | GlockApps | MXToolbox | Mail-Tester |
|---|---|---|---|---|
| Entry price | Free forever (core) | $59/mo minimum | $129/mo (deliverability) | 3 free/day, $22/mo |
| Top tier | Paid (priority/retention) | $399/mo (agency) | $599/mo (advanced) | Paid tier |
| Seed network | 4,000+ | ~100–200 | Small (auth-focused) | 1 mailbox per provider |
| Provider coverage | 30+ incl. CIS, ProtonMail, iCloud, GMX, Zoho | Broad; weak on CIS | Auth-focused | Single seed per provider |
| Gmail folder detail | Primary/Promotions/Updates/Social/Spam | Inbox/Spam/Missing | n/a | n/a |
| API + MCP + A2A | Free public API, OAuth, MCP, A2A | API on higher tiers | API on higher tiers; no MCP | Limited API; no MCP |
| Post-send tracking | Per-seed, up to 72h | Delivery-time snapshot | Delivery-time only | Delivery-time only |
| Presend analyzer | 3-tier (deterministic + AI + link intel) | Stop-word list | Not offered | Spam-score components |
Price
- Inbox Check: $0 forever for core. Paid tier for priority/retention only.
- GlockApps: $59/mo minimum, $399/mo for agency features.
- MXToolbox: $129/mo for deliverability monitoring, $599/mo for advanced.
- Mail-Tester: 3 free/day, $22/mo for more.
Seed network size
- Inbox Check: 4,000+.
- GlockApps: ~100–200 (disclosed in marketing).
- MXToolbox: small placement footprint (not the core product).
- Mail-Tester: single mailbox per provider, then analytics.
Provider coverage
- Inbox Check: 30+ including Mail.ru, Yandex, Rambler, ProtonMail, iCloud, GMX, Zoho.
- GlockApps: broad; weaker on CIS providers.
- MXToolbox: auth-focused; less relevant here.
- Mail-Tester: single-seed per provider, so coverage equals “which providers they have one seed on”.
Gmail folder detection
- Inbox Check: Primary / Promotions / Updates / Social / Spam per seed.
- GlockApps: Inbox / Spam / Missing.
- MXToolbox: n/a.
- Mail-Tester: n/a.
API, MCP, A2A
- Inbox Check: free public API, OAuth, MCP server, A2A endpoint.
- GlockApps: API on higher tiers.
- MXToolbox: API on higher tiers; no MCP.
- Mail-Tester: limited API, no MCP.
Post-send tracking
- Inbox Check: yes, per-seed, up to 72h.
- GlockApps: delivery-time snapshot.
- Others: delivery-time only.
Presend analysis
- Inbox Check: 3-tier (deterministic + AI perception + link intel).
- GlockApps: stop-word list.
- Mail-Tester: spam score components.
- MXToolbox: not offered.
Run your own head-to-head
Run the same draft through Inbox Check and any competitor. The comparison is the evaluation — not this post.
FAQ
Is free always worse?
Only if the team behind free is pessimistic about the product. We're optimistic — the seed network is growing, the API is mature, the MCP/A2A surface is an active investment. The free path isn't a minimal product.
What's the strongest case for a paid competitor?
If you need a specific feature we don't ship yet (e.g., certain enterprise tenant-specific M365 diagnostics). Our default is 'we probably cover it' — check the provider list.
Do you take customer data from tests?
We retain hashed body + metadata for abuse detection and trend analysis. Never resold. API token holders can opt out of retention.
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