InboxDoctor
Per-mailbox warming from $2, with placement tests sold as credits
InboxDoctor is an email warming and deliverability platform that ramps sending volume on connected mailboxes through a network of inboxes the vendor describes as human-powered, and sells inbox placement tests, email health checks, and provider seed lists as separate credit packs; it is primarily a warming tool with placement testing attached, and it does not ingest DMARC aggregate reports or manage authentication policy.
Overview
InboxDoctor does the first job in this category, inbox warming, and attaches a piece of the second, placement testing, as a credit-based add-on. The warming engine connects to your sending mailboxes and exchanges messages with a network of other inboxes, ramping daily volume on a curve and generating the opens, replies, and spam rescues that teach mailbox providers a new sender is behaving like a real correspondent. What it does not do is authentication monitoring: it will not tell you who else is sending as your domain, and it has no path to a p=reject DMARC policy.
The pricing is the clearest in the warming market and unusually cheap. B2B plans are quoted per mailbox per month: Starter at $2 for thirty warmup emails a day, Growth at $4 for fifty, and Enterprise at $6 for a hundred, with discounts of ten to twenty percent for quarterly through annual commitment. Five mailboxes on Growth is $20 a month. Fifty mailboxes on Growth is $200 a month, or $100 on Starter. That per-mailbox model is transparent and it also scales linearly, which is the opposite of TrulyInbox's approach of charging by daily volume and allowing unlimited accounts.
There is a separate and much more expensive B2C ladder, at $120, $240, and $720 a month per mailbox for five hundred, one thousand, and three thousand warmup emails a day, aimed at high-volume consumer senders rather than sales teams. Placement testing is bought as credits, from $15 for a hundred to $1,000 for ten thousand, with email health test credits priced lower, and provider seed lists across Gmail, Outlook, Yahoo, and iCloud quoted on request. A seven-day free trial with no credit card and self-serve signup make evaluation straightforward.
The caveat that belongs on every warming product belongs here too, and buyers should read it before spending anything. Automated warming is contested practice. It manufactures engagement signals that do not correspond to real correspondence, mailbox providers have grown steadily better at recognizing artificial reciprocal traffic, and Google in particular has publicly discouraged it. Warming is best understood as a volume-ramp discipline for genuinely new mailboxes that will go on to send real mail people want, not as a way to make bad sending work. No vendor can independently prove the quality of its network, and InboxDoctor's is no exception.
Best for
Cold outbound teams and agencies running many sending mailboxes who want the cheapest transparent per-mailbox warming available, with placement testing bought as needed rather than bundled into a larger subscription.
Not the right fit for
- Anyone looking for DMARC monitoring or authentication policy management; InboxDoctor does not ingest aggregate reports and cannot get you to p=reject, which is a job for EasyDMARC, PowerDMARC, or DMARCLY.
- Senders who believe warming will rescue a bad list or bad copy; artificial engagement does not survive contact with real recipients marking mail as spam.
- Buyers who want unlimited mailboxes on a flat plan; the per-mailbox model scales linearly, so fifty mailboxes costs ten times what five costs, where TrulyInbox charges by daily volume instead.
- Marketing teams sending newsletters from an established domain; warming is for new or damaged sending identities, and an established sender gains little from manufactured traffic.
- Organizations that need a mature vendor relationship; InboxDoctor is an unfunded company founded in 2024, which is early even by this category's standards.
How it works
- 1
You connect a sending mailbox over Google Workspace, Microsoft 365, or SMTP and IMAP. The platform begins sending small volumes of conversational messages from that mailbox into its network and receiving messages back.
- 2
Daily volume ramps on a schedule set by your plan, from thirty a day on Starter up to a hundred on the B2B Enterprise tier. Messages that land in spam within the network are opened and moved to the inbox, which is the specific signal warming is trying to generate, and replies are exchanged so the traffic resembles a thread rather than a broadcast.
- 3
Custom templates and language selection let the warming content resemble the kind of mail you actually send, and Google Postmaster integration surfaces the reputation data Google publishes about your domain alongside the warming activity.
- 4
Separately, you buy credits to run inbox placement tests and email health checks. Placement tests send your real content to seed addresses across providers and report where copies landed; health tests check the technical posture of a domain or mailbox. These are metered independently from the warming subscription.
Feature breakdown
20 features in 4 modulesWarming engine
The core job: ramping a new mailbox to sending volume without tripping filters.- Network-based warming
- Connected mailboxes exchange messages with a network of inboxes the vendor describes as human-powered rather than simulated. As with every warming vendor, network composition cannot be independently audited by a buyer.
- Graduated daily volume
- Thirty warmup emails a day on Starter, fifty on Growth, and a hundred on the B2B Enterprise plan, which corresponds to nine hundred, fifteen hundred, and three thousand a month per mailbox.
- Spam rescue
- Messages landing in a network recipient's spam folder are opened and moved to the inbox, which is the specific signal warming exists to produce.
- Reply generation
- Warming traffic includes replies so the pattern resembles conversation rather than one-way sending, which is what filters are looking at.
- Custom templates
- Warming content can be shaped to resemble your real mail rather than generic filler, available on every tier including Starter.
- Language selection
- Warming in the language you actually send in, which matters for non-English senders whose real traffic would otherwise look nothing like their warmup.
Placement and health testing
Bought as credits rather than bundled, which keeps the warming price low.- Inbox placement test credits
- Packs from $15 for a hundred credits to $1,000 for ten thousand, run against seed addresses to report inbox, tab, or spam placement per provider.
- Email health test credits
- Cheaper packs from $10 to $820 covering technical posture checks on a domain or mailbox, separate from placement testing.
- Provider seed lists
- Seed list plans covering Gmail, Outlook, Yahoo, and iCloud, priced on request rather than published, which is the least self-serve part of the product.
- Google Postmaster integration
- Surfaces the domain reputation, spam rate, and authentication data Google publishes, included on every B2B tier including the $2 Starter plan.
- Testing cadence under your control
- Because tests are credit-metered rather than plan-limited, you decide how often to test; a hundred credits is enough for regular checks on a small sending estate.
Accounts and scale
Transparent per-mailbox pricing, plus a separate high-volume consumer ladder.- Per-mailbox B2B pricing
- $2, $4, and $6 per mailbox per month across Starter, Growth, and Enterprise, which is the cheapest published per-mailbox warming rate in the category.
- Separate B2C plans
- Essential, Pro, and Brand at $120, $240, and $720 a month for five hundred, one thousand, and three thousand warmup emails a day, aimed at consumer senders rather than sales teams.
- Commitment discounts
- Ten percent quarterly, fifteen percent semi-annually, and twenty percent annually, applied to the per-mailbox rate.
- Seven-day free trial
- No credit card required, with self-serve signup through the application.
- Support tiering
- Email support on Starter, live chat from Growth, and priority support with a dedicated account manager on Enterprise.
Mailbox connectivity
What you can connect, and what it means for a mixed sending estate.- Google Workspace connection
- Direct connection for Gmail and Workspace mailboxes, the most common sending infrastructure for outbound teams.
- Microsoft 365 connection
- Support for Outlook and Microsoft 365 mailboxes, where filtering behaves differently enough from Google to be worth warming separately.
- SMTP and IMAP support
- Generic connection for mailboxes outside the two major providers, which is how agencies handle client infrastructure they do not control.
- Per-mailbox independence
- Each mailbox is warmed and billed independently, so adding or removing a sending identity is a linear change rather than a plan migration.
Use cases
4 documentedOutbound agency spinning up client mailboxes
A new client campaign needs twelve fresh mailboxes across three domains, and sending from them cold would burn the domains within a week.
Twelve mailboxes on the $4 Growth tier costs $48 a month, ramping each to fifty warmup emails a day over several weeks before real campaign volume starts, with placement credits used to confirm readiness.
Founder recovering a damaged sending domain
A poorly targeted campaign produced spam complaints and the domain's mail now lands in junk even for existing conversations.
Warming plus Google Postmaster data shows the spam rate trend, and placement test credits track recovery per provider, though the honest answer is that recovery depends far more on stopping the bad sending than on the warming itself.
Sales team scaling from five to fifty mailboxes
Volume needs to grow tenfold and the team wants to know the warming cost before committing.
The per-mailbox model makes the arithmetic trivial: $20 a month at five mailboxes on Growth becomes $200 at fifty, with an annual commitment taking twenty percent off. TrulyInbox's daily-volume model may cost less at that scale, and should be priced against it.
Consumer brand sending high daily volume
A B2C sender needs warming at thousands of messages a day rather than the tens that a sales mailbox needs.
The separate B2C ladder at $120 to $720 a month per mailbox covers five hundred to three thousand warmup emails a day, which is a different product economically from the $2 B2B plan.
Pricing
from $2 per mailbox per month (B2B Starter)Per-mailbox monthly subscription for B2B warming with a separate high-volume B2C ladder, plus credit packs for placement and health testing.
| Plan | Price | Includes |
|---|---|---|
| Starter (B2B) | $2 per mailbox per month |
Five mailboxes costs $10 a month, fifty costs $100. The cheapest published per-mailbox warming rate in the category. |
| Growth (B2B) | $4 per mailbox per month |
Five mailboxes costs $20 a month, fifty costs $200. The tier most outbound teams should model. |
| Enterprise (B2B) | $6 per mailbox per month |
A hundred warmup emails a day is more than most sales mailboxes should be sending in total, so this tier is for aggressive ramps. |
| Essential, Pro, and Brand (B2C) | $120, $240, and $720 per month |
A separate product economically, aimed at consumer senders rather than sales teams. |
Add-ons
- Inbox placement test credits ($15 to $1,000): Packs from 100 to 10,000 credits.
- Email health test credits ($10 to $820): Packs from 100 to 10,000 credits, cheaper than placement testing.
- Provider seed lists (Quoted on request): Gmail, Outlook, Yahoo, and iCloud coverage; the one part of the product without published pricing.
Billing notes
- Per-mailbox pricing scales linearly, so fifty mailboxes costs ten times what five costs. At five mailboxes on Growth that is $20 a month, or $4 per mailbox; at fifty it is $200 a month, still $4 per mailbox.
- Commitment discounts run ten percent quarterly, fifteen percent semi-annually, and twenty percent annually, so fifty mailboxes on Growth billed annually is roughly $160 a month.
- Placement and health testing are credit packs bought separately, which keeps the warming subscription cheap but means the true cost of an evidence-based deliverability practice is higher than the headline per-mailbox figure.
- Seed list plans are the only element without published pricing, which slightly breaks the otherwise fully self-serve model.
- The B2C ladder is priced per mailbox at a different order of magnitude, so a consumer sender should not model costs from the B2B page.
- The seven-day trial requires no credit card, but seven days is short relative to the several weeks a proper warming ramp takes.
Value assessment: On the warming axis alone, InboxDoctor is the cheapest transparent option published anywhere in this category. Two dollars a mailbox for a thirty-a-day ramp, with Google Postmaster data and custom templates included at that price, undercuts MailReach, Warmbox, and Mailivery substantially. The linear model is honest and easy to budget, and it is also the weakness: at fifty mailboxes, TrulyInbox's volume-based pricing with unlimited accounts is likely to be cheaper, and the gap widens above that. Credit-based placement testing is a fair structure that keeps the base price low. The real question is not price at all but whether automated warming works well enough to be worth any money, which is a judgement no vendor's pricing page can settle.
Strengths & limitations
Strengths
- The cheapest published per-mailbox warming rate in the category, at $2 a mailbox for a thirty-a-day ramp.
- Completely transparent pricing that is trivial to model at any mailbox count, unlike volume-tier competitors.
- Google Postmaster integration included on every B2B tier including the $2 plan, giving you Google's own view of your domain reputation alongside the warming.
- Custom templates and language selection on all tiers, so warming content can resemble your real mail rather than generic filler.
- Placement and health testing sold as credits, so you pay for evidence when you need it rather than carrying a bundled subscription.
- Separate B2C ladder for high-volume consumer senders, a segment most warming tools ignore entirely.
- Seven-day trial with no credit card and fully self-serve signup.
Limitations
- Automated warming is contested practice. It manufactures engagement that does not correspond to real correspondence, mailbox providers have become better at detecting reciprocal warming networks, and Google has publicly discouraged it. Treat it as a volume-ramp discipline for genuinely new mailboxes, not a fix for bad sending.
- Network composition and quality cannot be independently verified by a buyer, here or at any warming vendor; the description of the network as human-powered is the vendor's claim rather than an audited fact.
- Per-mailbox pricing scales linearly, so large sending estates get expensive relative to volume-priced competitors like TrulyInbox.
- No DMARC aggregate report monitoring, so it says nothing about who else sends as your domain and offers no path to an enforced policy.
- Seed list plans are quoted on request, the one part of the offering without published pricing.
- The seven-day trial is short relative to a warming ramp, which takes several weeks to demonstrate anything.
- Founded in 2024 and unfunded, which is early even in a category full of small vendors, and worth weighing before you build a sending operation on it.
Head-to-head comparisons
6 alternativesInboxDoctor vs TrulyInbox
from $0 (Free), then $22 per month billed annually (Starter, $29 monthly)The two price warming in opposite ways. InboxDoctor charges per mailbox, from $2 to $6, so five mailboxes is $10 to $30 a month. TrulyInbox charges by total daily warmup volume with unlimited accounts, so $22 a month covers roughly three mailboxes and $169 covers roughly fifty. Below about ten mailboxes InboxDoctor is cheaper and simpler; above that TrulyInbox's model usually wins, and any team planning to scale should price both.
Full InboxDoctor vs TrulyInbox comparisonInboxDoctor vs MailReach
from $25/mailbox/moMailReach is the more established warming specialist with a longer track record and bundled spam placement testing, at a notably higher per-mailbox price. InboxDoctor is cheaper, newer, and sells testing separately as credits. Take MailReach if warming quality and vendor maturity justify the premium; take InboxDoctor if you are warming many mailboxes and want the lowest transparent per-mailbox cost.
Full InboxDoctor vs MailReach comparisonInboxDoctor vs Warmy
from $49/mailbox/moWarmy covers marketing and transactional senders on ESPs as well as sales mailboxes, with a broader automation story and higher pricing. InboxDoctor is focused on per-mailbox warming for outbound plus a separate high-volume B2C ladder. Choose Warmy for ESP-side sending and a wider platform; choose InboxDoctor for cheap per-mailbox ramping of sales infrastructure.
Full InboxDoctor vs Warmy comparisonInboxDoctor vs Unspam
from $0 (Free), then $9 per month (Basic)Unspam is a campaign sender's testing tool covering placement and cross-client rendering, with no warming at all. InboxDoctor warms mailboxes and sells placement tests as credits. If your problem is that a new mailbox has no reputation, InboxDoctor; if your problem is that a designed campaign is being filtered or rendering badly, Unspam.
Full InboxDoctor vs Unspam comparisonInboxDoctor vs GlockApps
from $59/mo (Essential, billed annually)GlockApps is the rigorous measurement platform, with a documented seed panel, multi-filter scoring, DMARC analytics, and blacklist monitoring, and no warming. InboxDoctor is the reverse: warming first, testing as an add-on. Serious deliverability practices often run both, using GlockApps for evidence and a warming tool for new sending identities.
Full InboxDoctor vs GlockApps comparisonInboxDoctor vs Warmup Inbox
from $15/inbox/mo (Basic, billed annually at $180/yr)Both are dedicated warming networks for outbound senders, and the decision comes down to per-mailbox economics and network behaviour rather than feature lists. InboxDoctor publishes the lowest per-mailbox rate in the category at $2 to $6 and bundles Google Postmaster data at every tier. Compare them on your actual mailbox count and on how conservative a ramp each one defaults to.
Full InboxDoctor vs Warmup Inbox comparisonImplementation & onboarding
- Setup time
- Fifteen minutes to connect a mailbox and start warming. Reaching meaningful volume takes three to six weeks of ramping, which is the real timeline and cannot be compressed by paying more.
- Learning curve
- Low. Connect mailboxes, choose a daily volume, and let it run. The judgement required is not operational but strategic: deciding whether warming is appropriate for your situation at all, and resisting the temptation to treat a good warming score as permission to send badly.
- Onboarding
- Self-serve through the application with a seven-day trial and no credit card. Live chat arrives at the Growth tier and a dedicated account manager at Enterprise.
- Migration notes
- Switching warming vendors means disconnecting mailboxes from one platform and connecting them to another; no history transfers, and the reputation you built stays with the mailbox rather than the tool. Avoid running two warming services on the same mailbox simultaneously, since the combined volume can look more artificial than either alone.
Platform, API & security
- Platforms
- Web applicationGoogle Workspace connectionMicrosoft 365 connectionSMTP and IMAP connection
- API
- Not published as a headline self-serve capability.
- Compliance
- GDPR
- Data residency
- Not published as a customer-selectable option.
- SSO
- Not offered on the published tiers.
- Security notes
- Warming requires granting the platform send and read access to your production sending mailboxes, which is a substantially larger trust decision than a testing tool asks for. Review the connection scopes before authorizing, particularly on Google Workspace, and prefer dedicated sending mailboxes over a mailbox that also holds sensitive correspondence.
Support & resources
- Channels
- Email support on StarterLive chat from GrowthPriority support and a dedicated account manager on Enterprise
- Documentation
- Product documentation and case studies covering warming setup, placement testing, and Google Postmaster interpretation.
- Community
- No large official user community.
Company
- Founded
- 2024
- Headquarters
- Wilmington, Delaware, United States
- Ownership
- Privately held and unfunded
- Founders
- Sumith Bangarwa
- Employees
- Not disclosed; small team
- Funding
- No disclosed outside funding.
Timeline
- 2024Founded by Sumith Bangarwa and registered in Delaware, entering an already crowded warming market on a per-mailbox pricing model rather than volume tiers.
- 2024The Google and Yahoo bulk sender requirements raise the cost of poor sending practice, expanding demand for deliverability tooling across small outbound teams.
- 2025Adds inbox placement and email health testing as credit packs alongside the warming subscription, plus provider seed lists across Gmail, Outlook, Yahoo, and iCloud.
- 2025Introduces a separate B2C ladder at $120 to $720 a month per mailbox for consumer senders warming at hundreds to thousands of messages a day.
- 2026Continues to publish the cheapest per-mailbox warming rate in the category at $2 a month, competing on price transparency against volume-priced rivals.
Integrations
- Google Workspace and Gmail
- Microsoft 365 and Outlook
- Generic SMTP and IMAP mailboxes
- Google Postmaster Tools
- Seed list providers across Gmail, Outlook, Yahoo, and iCloud
- Any sending platform, since warming operates on the mailbox rather than the sending tool
Frequently asked questions
10 questionsWhat is InboxDoctor?
InboxDoctor is an email warming platform. It connects to your sending mailboxes and exchanges messages with a network of inboxes, ramping daily volume and generating opens, replies, and spam rescues so mailbox providers learn to treat a new sender as legitimate. It also sells inbox placement tests, email health checks, and provider seed lists as separate credit packs.
Which of the three deliverability jobs does InboxDoctor do?
Primarily inbox warming, with placement testing available as a credit-based add-on. It does not do authentication monitoring: it does not ingest DMARC aggregate reports, will not tell you who else is sending as your domain, and offers no path to a p=reject policy. That work belongs to EasyDMARC, PowerDMARC, DMARCLY, or URIports.
How much does InboxDoctor cost per mailbox?
B2B warming is $2 per mailbox per month for thirty warmup emails a day, $4 for fifty, and $6 for a hundred. Five mailboxes on the $4 Growth plan is $20 a month. Fifty mailboxes on the same plan is $200 a month, or $160 with an annual commitment at the twenty percent discount. There is a separate B2C ladder at $120, $240, and $720 a month per mailbox for much higher daily volumes.
Is the warming network real mailboxes or simulated?
The vendor describes it as human-powered, meaning real inboxes rather than simulated traffic. That is the claim every warming vendor makes and none can prove to a buyer, because network composition is not independently auditable. Judge warming vendors on ramp behaviour, content realism, and whether their traffic pattern looks like conversation, and treat network quality claims across this whole category as unverifiable marketing.
Does email warming actually work?
It is contested, and an honest answer has to say so. Warming manufactures engagement signals that do not correspond to real correspondence, mailbox providers have become considerably better at recognizing reciprocal warming networks, and Google has publicly discouraged the practice. The defensible use is ramping a genuinely new mailbox gradually before it sends real mail that people want. The indefensible use is trying to make a bad list or bad copy deliverable, which warming will not achieve at any price.
How does placement testing work here and what does it cost?
Placement tests are bought as credit packs from $15 for a hundred credits to $1,000 for ten thousand, with cheaper email health test credits from $10. You send your real content to seed addresses and the platform reports where copies landed per provider. Seed list plans covering Gmail, Outlook, Yahoo, and iCloud are quoted on request rather than published, which is the least self-serve part of the product.
Does a good placement test mean my real recipients got the email?
No. Seed inboxes have no engagement history with you, while real recipients do, and mailbox providers personalize filtering heavily on that history. A clean seed result means nothing structural is wrong with authentication, content, or reputation. It does not prove a specific prospect saw your message. This caveat applies to every placement tester, not just this one.
What does InboxDoctor not do?
It does not send campaigns, verify or clean lists, monitor DMARC aggregate reports, manage authentication records, or render your email across clients. It warms mailboxes and, with credits, tests placement. Buyers frequently arrive with an authentication problem and buy a warming tool, or arrive with a warming problem and buy a DMARC tool. Diagnose which of the three jobs you actually need before spending.
Should I choose InboxDoctor or TrulyInbox?
It comes down to mailbox count. InboxDoctor charges per mailbox, so the cost is linear and predictable and very cheap at small counts: five mailboxes for $10 to $30 a month. TrulyInbox charges by total daily warmup volume with unlimited accounts, so it gets cheaper per mailbox as you scale, roughly $169 a month for around fifty mailboxes. Under ten mailboxes, InboxDoctor. Over twenty, price TrulyInbox first.
Who owns InboxDoctor?
InboxDoctor is a privately held, unfunded company founded in 2024 by Sumith Bangarwa and registered in Wilmington, Delaware. It is early-stage even by the standards of this category, which is worth weighing before making it a dependency of a sending operation, particularly since warming requires granting access to production mailboxes.
Editorial verdict
InboxDoctor is the cheapest transparent warming product on the market, and for a small outbound team the arithmetic is hard to argue with: five mailboxes ramping at fifty emails a day for $20 a month, with Google Postmaster data and custom templates included, and placement tests available as credits when you need evidence. The per-mailbox model is honest and easy to budget, and it is also the limitation, since linear scaling makes TrulyInbox's volume pricing cheaper above roughly twenty mailboxes. Two larger cautions apply. The company was founded in 2024, is unfunded, and asks for access to your production sending mailboxes, which is a real trust decision. And warming itself is contested practice that mailbox providers increasingly detect and Google has discouraged, so it should be used to ramp genuinely new mailboxes rather than to make bad sending work. Within those limits, this is a well-priced tool that does exactly one job.
Written by the SaaSTracker editorial team. Awards, when shown, are judged against the published criteria in our methodology.