InboxDoctor vs Warmup Inbox
An independent, review-free comparison compiled by the SaaSTracker editorial team. Both products are profiled in full, and neither can pay for placement here.
The short answer
Editorial assessmentInboxDoctor compared with Warmup Inbox
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.
Choose InboxDoctor if
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.
Choose Warmup Inbox if
Outbound teams and agencies that want per-inbox warming with high daily-volume headroom, real blacklist monitoring with delisting help, and warm-up customization (templates, topics, languages, ESP-specific patterns) for senders that need warming traffic to resemble their real mail.
Side by side
13 attributes| Attribute | InboxDoctor | Warmup Inbox |
|---|---|---|
| Category | Deliverability | Deliverability |
| Starting price | $2 per mailbox per month (B2B Starter) (7 days trial) | $15/inbox/mo (Basic, billed annually at $180/yr) (7 days trial) |
| Pricing model | Per-mailbox monthly subscription for B2B warming with a separate high-volume B2C ladder, plus credit packs for placement and health testing. | Per-inbox monthly subscription in three tiers that scale daily warm-up volume, reply rate, and feature depth; annual billing saves 20 percent, and custom agency plans start at 15 inboxes. |
| Free plan | No | No |
| Free trial | 7 days, no credit card required | 7 days, full access to the chosen plan, no credit card required up front |
| 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. | Outbound teams and agencies that want per-inbox warming with high daily-volume headroom, real blacklist monitoring with delisting help, and warm-up customization (templates, topics, languages, ESP-specific patterns) for senders that need warming traffic to resemble their real mail. |
| 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. | Minutes per inbox via OAuth or SMTP; the vendor claims 90 percent primary placement by day 14, but 2 to 4 weeks remains the realistic window before a new domain carries campaign volume. |
| 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. | Low on Basic, where defaults do the work; moderate on Pro and Max, where templates, topics, ESP-specific settings, and scheduling reward deliberate configuration. |
| Platforms | Web application, Google Workspace connection, Microsoft 365 connection, SMTP and IMAP connection | Web app, Developers API (all tiers, unlimited on Max) |
| Compliance | GDPR | GDPR-aligned processes with a published data processing agreement |
| Founded | 2024 | 2020 |
| Headquarters | Wilmington, Delaware, United States | Bratislava, Slovakia (operated by CyberPanda s.r.o., part of the itrinity portfolio) |
| Ownership | Privately held and unfunded | Owned by itrinity (acquired November 2021) |
Strengths and limitations
InboxDoctor
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.
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.
Warmup Inbox
Strengths
- Highest published per-inbox volume ceiling in its peer group (1,000 warm-up messages a day on Max), suited to warming infrastructure and aggressive senders.
- Blacklist monitoring across 100+ lists with delisting assistance is real remediation tooling, not just an alert feed.
- The Pro customization layer (custom templates, topics, language warm-up, ESP-specific patterns) makes warming traffic resemble actual sending better than generic warmers manage.
- API access on every tier, unlimited on Max, gives agencies and platforms a programmatic surface most competitors reserve for enterprise deals.
Limitations
- Per-inbox pricing compounds quickly; multi-mailbox teams pay multiples of what shared-pool or unlimited-mailbox competitors charge.
- Headline performance claims (98 percent primary placement, 90 percent by day 14) are self-reported vendor benchmarks with no independent audit.
- No seed-panel placement testing or DMARC analytics; measurement beyond warm-up traffic and list status requires a separate diagnostics tool.
- The bundled outreach-sequences feature is thin next to dedicated sequencers and should not factor into the buying decision.
Pricing compared
InboxDoctor
Per-mailbox monthly subscription for B2B warming with a separate high-volume B2C ladder, plus credit packs for placement and health testing.
- Starter (B2B)$2
- Growth (B2B)$4
- Enterprise (B2B)$6
- Essential, Pro, and Brand (B2C)$120, $240, and $720
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.
Warmup Inbox
Per-inbox monthly subscription in three tiers that scale daily warm-up volume, reply rate, and feature depth; annual billing saves 20 percent, and custom agency plans start at 15 inboxes.
- Basic$15 per inbox
- Pro$49 per inbox
- Max$79 per inbox
- Agency / volumeCustom
Warmup Inbox prices capability, not just quantity: $15 buys a competent standard warmer with monitoring, $49 buys the customization that makes warming traffic resemble your real mail, and $79 buys volume headroom (1,000/day) almost nobody else publishes. For one to a few inboxes that ladder is fair, and the blacklist monitoring with delisting help does work competitors charge separately for. The weakness is arithmetic: per-inbox billing compounds, and a 10-mailbox team at Pro pays $490 a month where Mailivery's Business tier covers unlimited mailboxes for $199. Buy Warmup Inbox for depth per inbox; buy elsewhere for breadth of inboxes.
Editorial verdict on each
InboxDoctor
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.
Read the full InboxDoctor profileWarmup Inbox
Warmup Inbox is the depth-per-inbox pick among warming networks. The Pro customization layer and Max's 1,000-a-day ceiling solve real problems generic warmers cannot (non-English senders, ESP-specific patterns, infrastructure warming), and blacklist monitoring with delisting help plus an API on every tier make it operationally serious for a tool starting at $15. Its structural weakness is the meter: per-inbox billing turns a large mailbox roster into a large invoice, exactly the scenario shared-pool and bundled-warming competitors are built to win. Choose Warmup Inbox to warm a limited set of inboxes hard and watch their reputation properly; choose Mailivery or a sequencer's built-in warming when mailbox count, not warming depth, is the problem.
Read the full Warmup Inbox profileInboxDoctor profile last reviewed 2026-08-22; Warmup Inbox last reviewed 2026-08-22. Pricing is compiled from public sources and can change without notice. See our methodology.