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InboxKit vs Infraforge: Bundled IP Pricing vs Unbundled Line Items
Both ship dedicated-IP sending, but they bill it in opposite ways. InboxKit folds the IP cost into a flat per-mailbox rate. Infraforge meters the IP as a separate line. The structural difference shapes who fits each model.
The Verdict
This comparison is uniquely about pricing structure, not isolation capability. Both InboxKit and Infraforge deliver dedicated-IP sending at the entry level, so the question of "do I get my own IP" is settled at both providers. What is not settled is how each provider exposes the IP economics to the buyer.
InboxKit bundles the IP into its tier rates (Professional $31 for 10 mailboxes, Agency $81 for 30, Enterprise $250 for 100), with per-mailbox effective costs from $3.10 down to $2.50 depending on tier; the IP cost is invisible inside the per-mailbox total within each tier. Infraforge meters the IP as an explicit $99/mo line item separate from the per-mailbox SMTP fee, with SSL and domain masking also metered separately at $2 per domain. The tiered-with-bundled-IP model is easier to predict and budget.
The unbundled line-item model gives compliance-led buyers granular control over which components they purchase. Both are legitimate billing strategies. The choice maps to whether your buying process prefers a single tier rate or itemized component selection.
InboxKit vs Infraforge
| Feature | InboxKit | Infraforge |
|---|---|---|
| Pricing | ||
| Price per Mailbox | $3.10-$2.50 by tier Professional $31/mo (10 slots), Agency $81/mo (30 slots), Enterprise $250/mo (100 slots). Verifier, placement testing, blacklist checker in base. Warmup +$3/mailbox add-on. | $3-$4/mo Per-mailbox rate before add-ons |
| Dedicated IP Cost | Included US-based IPs included in the per-mailbox rate | $99/mo extra Dedicated IP is a $99/mo add-on |
| Cost for 100 Mailboxes | $250/mo 100 x $2.50, all tools included | $350-$499/mo 100 x $3.50 avg + $99 dedicated IP |
| Infrastructure | ||
| Mailbox Types | GWS + M365 + Azure Google Workspace, Microsoft 365, and Azure | SMTP only Dedicated IP SMTP mailboxes |
| Multi IP Provisioning | Not specified IP allocation details not published | Yes Provision multiple dedicated IPs |
| Deliverability | ||
| Pre-warmed Domains | Built-in warmup Warmup tool included in platform | Yes Pre-warmed domains for faster ramp-up |
| Inbox Placement Testing | Yes Built-in placement testing | No Not available natively |
| Email Verifier | Yes Built-in email verification | No Not available natively |
| Features | ||
| Masterbox | Dedicated panel per domain Domain-level monitoring panels | Yes Centralized masterbox for management |
| Domain Masking | Not specified Not mentioned | $2/domain/mo SSL and domain masking at $2 per domain per month |
Bundled flat-rate vs unbundled line-item billing
These two providers have made opposite billing strategy choices and the choice shapes who their pricing fits best. InboxKit's model is tiered: Professional $31/mo for 10 mailbox slots (extra at $3.10), Agency $81/mo for 30 slots (extra at $2.70), Enterprise $250/mo for 100 slots (extra at $2.50). The mailbox, IP, placement testing, verifier, and blacklist checker are bundled at the tier rate.
Email Warmup is a separate $3/mailbox add-on. Within a tier, the bill is predictable; tier transitions are where the per-mailbox math shifts. There is one tier-rate to track and one upgrade decision when you grow.
Infraforge's model is line-item: $3-$4 per mailbox covers the SMTP layer and platform features but the $99/mo dedicated IP is its own line and the $2/domain SSL/masking is its own line. You provision exactly the components you need; you negotiate each line if your usage justifies it. The trade-off: the bill is harder to estimate before you fully model your domain count and IP allocation needs.
Neither model is universally correct. Operations-led buyers usually prefer InboxKit's tiered model because tier selection and the few add-on decisions are simpler to budget. Compliance-led buyers usually prefer Infraforge's line items because the audit trail is cleaner when each component is named.
Key takeaways
- InboxKit bundles IP, verification, placement testing, and blacklist monitoring into tier rates ($31/$81/$250); warmup is +$3/mailbox add-on
- Infraforge meters IP ($99), SSL/masking ($2/domain), mailboxes ($3-$4) separately
- Flat rate eliminates billing variability for ops-led buyers
- Line items provide audit-friendly itemization for compliance-led buyers
How each pricing model scales with fleet size
The two models behave differently at different fleet sizes: At 25 mailboxes: InboxKit Agency is $81 + 0 extras (still under the 30-slot inclusion). Infraforge is roughly $187/mo (25 x $3.50 + $99 + ~5 domains x $2). The InboxKit tier wins at this size because Infraforge's fixed IP fee dominates.
At 100 mailboxes: InboxKit Enterprise is $250/mo (the 100-slot tier exactly). Infraforge is roughly $489/mo (100 x $3.50 + $99 + 20 x $2). InboxKit still wins but the gap narrows because the Infraforge IP fee amortizes better at this size.
At 300 mailboxes: InboxKit Enterprise is $250 + 200 extras at $2.50 = $750/mo (warmup add-on would add $900 more if needed). Infraforge is roughly $1,249/mo (300 x $3.50 + $99 + 50 x $2 + potentially volume discount). InboxKit still wins on infrastructure cost; large fleets on Infraforge often negotiate the per-mailbox rate down to $3.00 or below.
The pattern: tier-based pricing is consistently lower across the curve, but the gap narrows at scale where Infraforge's line-item negotiability creates more downside flexibility. At 500+ mailboxes, InboxKit volume discounts kick in via custom pricing.
Key takeaways
- At 25 mailboxes: InboxKit Agency $81 (under 30-slot tier) vs Infraforge ~$187
- At 100 mailboxes: InboxKit $250 vs Infraforge ~$489
- At 300 mailboxes: InboxKit $750 vs Infraforge ~$1,249 (before negotiation)
- Flat rate consistently lower; gap narrows at scale
When the unbundled model wins on multi-IP isolation
There is one scenario where Infraforge's line-item model produces genuinely different outcomes from InboxKit's flat-rate: multi-IP isolation across campaigns or clients. Infraforge lets you provision multiple IP blocks ($99 each) and allocate mailboxes across them. An agency running three client books can isolate each client's reputation by allocating each book to a separate IP block.
This costs $297/mo in IP fees but gives clean per-client reputation isolation that satisfies audit requirements. InboxKit's bundled IP model allocates IPs at the mailbox level rather than at the block level. Multi-client isolation is achievable but the configuration is less explicit, which matters for buyers whose compliance reviewers want to see the IP allocation logic on paper.
For in-house teams running their own outbound, the multi-IP isolation feature rarely justifies the higher Infraforge bill. For agencies and B2B2B vendors, it sometimes does. The decision turns on whether your compliance posture requires explicit per-cohort IP separation.
Key takeaways
- Infraforge: multiple $99 IP blocks for explicit per-cohort isolation
- InboxKit: per-mailbox IP allocation, less explicit but achievable
- In-house teams rarely benefit from multi-IP block isolation
- Agencies and B2B2B vendors sometimes do
Deliverability features in the box vs sold separately
InboxKit includes inbox placement testing, email verifier, and blacklist checker inside its tier rates ($31 Professional, $81 Agency, $250 Enterprise). These features run native to the platform; there is no separate subscription to manage. Email Warmup is a separate $3/mailbox add-on across all tiers.
Infraforge ships pre-warmed domains (a one-time provisioning event) but does not include an ongoing warmup tool. Inbox placement testing is not included. Verification is not included.
Blacklist monitoring is not included. Teams running Infraforge typically pair it with a sender tool that provides those capabilities; SendKit's native suite is one option, third-party warmup tools are another. The bundling difference creates a real total-cost gap at any volume.
A Mailforge-style spec sheet might omit these features entirely; InboxKit's tier price assumes you wanted the non-warmup tools, while warmup is a deliberate add-on decision.
Key takeaways
- InboxKit bundles warmup, placement testing, verification, blacklist monitoring
- Infraforge ships pre-warming once but no ongoing warmup tool
- Verification, placement testing, blacklist monitoring sold elsewhere on Infraforge
- The bundling gap is the largest real-cost difference between the two
Pros & Cons
InboxKit
Strengths
- Nearly half the cost of Infraforge at 100 mailboxes
- Google Workspace + Microsoft 365 + Azure vs SMTP only
- Built-in warmup, placement testing, verifier, blacklist checker
- US-based IPs included in the flat per-mailbox rate
- No separate add-on fees for IP or masking
Limitations
- No multi IP provisioning feature mentioned
- Less granular IP allocation control
- Not part of the Salesforge ecosystem
Infraforge
Strengths
- Multi IP provisioning for granular campaign isolation
- Pre-warmed domains for fast ramp-up
- Masterbox for centralized management
- Upgrade path from Mailforge (shared to dedicated)
- API access for automation
Limitations
- Significantly more expensive at scale ($489/mo vs $250/mo at 100 mailboxes)
- Dedicated IP costs $99/mo extra on top of per-mailbox pricing
- SSL and domain masking adds $2/domain/mo
- SMTP only, no Google Workspace or Microsoft 365
- No built-in deliverability monitoring tools
Got questions? We've got answers.
The InboxKit tier model wins decisively at small fleets because the Infraforge unbundled IP fee dominates the bill. At 25 mailboxes, InboxKit Agency is $81/mo (still inside the 30-slot tier) while Infraforge is roughly $187/mo because the $99 IP fee amortizes over too few mailboxes. InboxKit's tiered pricing is consistently cheaper across the volume curve up to 300+ mailboxes, but the gap narrows at scale where Infraforge enterprise negotiations are possible.
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