Compare/Head to head

InboxKit vs Warm Inboxes

Same facts, side by side: starting price, free tier, MCP, API and what each one is actually built for.

Starting price

InboxKit

$2.50/mailbox/mo

US-IP Google Workspace and Microsoft 365 mailboxes for cold email, with SPF, DKIM and DMARC set up for you and export to 24+ sequencers. One flat rate per mailbox: $3.00 a month, or $2.50 on annual billing, with no plan or minimum.

Where InboxKit fits

  • Agency recruiters sending cold email to hiring managers at volume
  • Teams already sequencing in Instantly, Smartlead, Lemlist or Apollo
  • Teams that want to automate mailbox setup through an API

Warm Inboxes

$3/inbox/mo

Cold email sending infrastructure: prewarmed Google, Microsoft 365 and Azure inboxes on free domains that can send the day you buy them, and cheaper fresh inboxes on your own domains for scaling. Fresh inboxes start at $3 a month and prewarmed ones at $8 a month each.

Where Warm Inboxes fits

  • Agency recruiters launching cold business development email fast
  • Teams whose sending domains got burned mid-campaign
  • Desks scaling outreach across many inboxes
  • Instantly and Smartlead users who want inboxes set up for them

At a glance

DetailInboxKitWarm Inboxes
Starting price$2.50/mailbox/mo$3/inbox/mo
Free tier–No–No
MCP server–No–No
Public API✓Yes–No
Listed underDeliverabilityDeliverability

Where they pull apart

InboxKit

Stands out: Each domain gets its own isolated admin panel, so one damaged domain does not drag the others down. A full REST API with webhooks lets agencies provision mailboxes automatically when a new client signs, and an Azure option covers up to 100 mailboxes for $30 a month.

Watch out: Warmup is not included: it is a $3 per mailbox a month add-on, more than the annual mailbox price itself. The $2.50 rate needs annual billing, and there is no free trial, though you can start with a single mailbox. The 90%+ inbox placement figure is the vendor's own claim.

Not the right fit for

  • Recruiters sending a handful of emails a day from their own inbox
  • Teams that want warmup and sending included in one price

Warm Inboxes

Stands out: Prewarmed inboxes skip the two to three week warmup, so a recruiting desk can start a business development campaign the same day or swap in fresh senders when a domain burns mid-campaign. The setup is already done: domains, SPF, DKIM, DMARC and forwarding are configured before you log in.

Watch out: Prewarmed inboxes sit on domains the vendor supplies, not your brand, and cost more than double a fresh inbox. Every result on the site comes from the vendor's own customer stories. It is infrastructure only, so you still need a sequencer such as Instantly or Smartlead.

Not the right fit for

  • Recruiters who only send from their main company mailbox
  • Teams that want inboxes on their own brand from day one at the lowest price
  • Buyers looking for a sequencer or lead database

Pros and cons

InboxKit

  • Same price for Google and Microsoft mailboxes
  • No plans, slots or minimums
  • Full API with webhooks
  • Warmup costs extra
  • No free trial
  • No sequencer of its own

Warm Inboxes

  • Prewarmed inboxes send on day one
  • DNS and authentication set up for you
  • Same-day replacement inboxes when a domain burns
  • Prewarmed inboxes use vendor-supplied domains
  • Results quoted are the vendor's own
  • Needs a separate sending tool

What each one costs

InboxKit

$2.50/mailbox/mo

InboxKit charges one flat rate per mailbox, with no plans, no minimum and no base fee. Google Workspace and Microsoft 365 mailboxes cost the same: $3.00 a month on monthly billing, $2.70 on quarterly and $2.50 on annual. Azure is billed per tenant at $30 a month for up to 100 mailboxes. Isolated warmup is an add-on at $3 per mailbox a month, and the InfraGuard monitoring add-on has its first month free. You pay from a prepaid wallet. Confirm current terms on the vendor site.

Checked 30 Sep 2026

Warm Inboxes

$3/inbox/mo

Prices are per inbox per month. Prewarmed Google or Microsoft inboxes come in packs of 3 with a free prewarmed .com domain at $8 an inbox monthly, $7 on 2-month or $6 on quarterly billing; a prewarmed Azure tenant of 100 inboxes is $69 a month. Fresh inboxes on your own domains need a 14 to 21 day warmup: Google Workspace from $3.50 an inbox monthly (down to $2 yearly at 100+ inboxes) and Microsoft 365 from $3 monthly ($2 yearly). Creating an account needs no card. Confirm current terms on the vendor site.

Checked 19 Oct 2026

Common questions

Is InboxKit cheaper than Warm Inboxes?
InboxKit starts lower, at $2.50/mailbox/mo against $3/inbox/mo for Warm Inboxes. That is the entry plan on each side, so the real number depends on seats and the tier you land on.
Can you try InboxKit or Warm Inboxes for free?
Neither carries a free tier on our listing.

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Editorial listings, never paid rankings. Prices checked 30 Sep 2026. Confirm current terms on the vendor site. Spot an error?