WarmupInbox

Warmup Inbox does one job: it exchanges email between your sending mailbox and a network of other mailboxes so that providers see engagement on your domain before you start cold outreach. It is not a sender, not a CRM and not a verifier. Whether a single-purpose warmup tool is worth a separate line item, when Woodpecker and Smartlead both bundle warmup free, is the question this review exists to answer — and it is not one a feature list can settle.

We have not tested it yet. Everything below comes from Warmup Inbox’s own pricing page and documentation, checked in September 2026, and is reported as what the vendor states rather than what we have measured. There is no score on this page and there will not be one until the benchmark has run.

Pricing

This is the most important thing to understand about the product, and it is easy to miss: Warmup Inbox is priced per inbox, not per account. The headline $15/month is for one mailbox.

• Basic — $15/inbox/month ($180/year). 75 warmup messages a day, replies to your warmup mail at up to 25%.
• Pro — $49/inbox/month ($588/year). 250 messages a day, replies up to 45%, plus your own templates, warmup topic selection, language warmup, ESP-specific warmup and scheduling.
• Max — $79/inbox/month ($948/year). 1,000 messages a day, replies up to 50%, technical setup check and unlimited API.

Annual billing is 20% off across all three. There is a 7-day free trial with no card required.

The per-inbox model matters because cold email is a many-mailbox discipline. A standard setup of eight inboxes across two domains costs $120/month on Basic and $392/month on Pro — the cost scales linearly with precisely the thing you bought the tool for. Warmup Inbox does offer volume pricing from 15 inboxes and larger discounts past 50, but those rates are quoted on a call rather than published, so we cannot tell you what they are.

The network

Warmup Inbox’s argument is about the quality of the mailboxes doing the warming. It states a network of 30,000+ real inboxes across 25+ providers, sending roughly 6 million warmup emails a day, and contrasts this with competitors’ “shared pools of fake mailboxes” and “scripted engagement providers learn to filter”.

That distinction is plausible and it is also unfalsifiable from the outside. We cannot see the network, and neither can you. What we can do is measure whether inbox placement actually improves on domains warmed with it versus domains warmed elsewhere, which is what the benchmark is for.

Blacklist rescue

The genuinely uncommon feature. Warmup Inbox monitors 100+ blacklists daily and states that when an inbox is listed, delisting runs automatically — its own framing is that “most warmup tools tell you that you are listed; we get you delisted.”

If that works as described it is worth more than the warmup itself to anyone sending at volume, because a Spamhaus listing stops a campaign dead and the delisting process is otherwise a manual errand. It is high on the list of things to verify.

The numbers the vendor publishes

Warmup Inbox publishes specific comparative claims, each labelled on its own site as an internal benchmark:

• 98% primary placement versus 83% for “other warmup tools (average)”
• +15% more email in Primary than other warmup tools
• 90% primary placement by day 14, “other tools aren’t there by day 30”
• 34% reply rate across the network

We are reproducing these because they are the vendor’s actual claims and you deserve to see them, not because we endorse them. A vendor measuring itself against unnamed competitors, on its own infrastructure, with its own methodology, is not evidence — it is marketing that happens to contain numbers. These four figures are precisely what our benchmark will test, and if they hold up we will say so.

Setup and integrations

Connection is OAuth for Gmail, Google Workspace and Outlook, or plain SMTP for anything else, with a stated 60-second setup. Brand-new domains and established ones are both supported. Deliverability tracking covers inbox, spam and bounce rates, with DNS, SPF and DKIM checks built in. A developer API is available on all tiers, unlimited on Max.

Who it suits

The case for a standalone warmup tool is strongest when warmup quality is your bottleneck and you are running few enough mailboxes that per-inbox pricing stays sane — or when you are on a sender whose bundled warmup you have specific reason to distrust. The case is weakest when you already pay for a sender that includes warmup at no extra cost, which most of this category now does.

What we’ll test

Inbox placement on identically configured domains, one warmed with Warmup Inbox and one with the warmup bundled into the sender, over 30 days from the same cold campaign. That comparison is the only way to know whether a separate line item buys anything. We will also try to trigger a blacklist rescue. Until then this page carries facts and no verdict — the method is on how we test.