Lemwarm vs Warmbox: Email Warmup Tool Comparison

Lemwarm is the email warm-up tool made by lemlist, sold at a flat price per mailbox and included free with every lemlist plan. Warmbox, its closest standalone rival, sells inboxes in threes. Its plans carry 1, 3 and 6 inbox warm-ups, and a team that needs a seventh is talking to sales instead of paying a little more. Lemwarm sells them one at a time at a flat $29 each. That difference in shape, more than any feature on either page, is what decides this pair, and it means the cheaper tool changes twice as your mailbox count grows.

What is Lemwarm?

Lemwarm is lemlist's email warm-up service. It connects to a mailbox and exchanges automatic warm-up emails with a network its pricing page describes as 20k+ healthy domains, so that a new or damaged sender builds a normal looking history before cold campaigns go out. The Essential plan is $29 per email account a month, or $24 billed yearly. The Smart plan is $49, or $40 yearly. Lemwarm's own pricing page also says you get lemwarm free with lemlist, so a lemlist customer comparing the two already owns it.

The short answer

Pick Warmbox if your mailbox count sits at or just under one of its plan boundaries. At exactly 3 inboxes it is $79 against Lemwarm's $87, and at exactly 6 it is $159 against $174. Its plan cards differ only in capacity and in support level, with Premium support on Solo and Start-up and Enterprise support on Growth.

Pick Lemwarm if your mailbox count is awkward, if it grows steadily, or if you are on lemlist. One mailbox costs $29 on Lemwarm and $19 on Warmbox Solo, but two mailboxes cost $58 on Lemwarm and $79 on Warmbox, because the second one forces the Start-up plan. Above six inboxes Warmbox stops publishing a price entirely and Lemwarm keeps charging $29 a mailbox.

And the exception that decides it for a lot of readers: every lemlist plan includes lemwarm, so lemlist customers already own one of these.

One tool prices a mailbox, the other prices a bracket

Lemwarm pricing

The page carries three billing periods rather than two: monthly, quarterly at 10% off and yearly at 20% off.

Source: Lemwarm pricing

Warmbox pricing

Team members are capped to the same number as inboxes on each tier, which is an easy detail to miss when sizing for an agency.

Source: Warmbox pricing

The arithmetic, and the two places the ranking flips

Here is an invented but arithmetically honest worked example. The inbox counts are chosen to show where the two curves cross. No part of it comes from a customer, and both rates are the published ones on monthly billing.

That is a genuinely unusual shape. The answer alternates, because a flat line and a staircase cross every time the staircase steps. Warmbox wins wherever your count lands exactly on a boundary and loses in the gap just above one.

The practical reading is not to memorise the table. It is that Warmbox rewards a mailbox count you control and punishes one that drifts, while Lemwarm is indifferent to where the count sits. An agency adding a client mid-month feels that difference immediately.

Above six inboxes the comparison stops being arithmetic, because Warmbox's pricing page gives its Team plan no rate. A team at that size is comparing a known $29 a mailbox against a quote.

The daily ceilings are published on one side only

Price is not the only thing a warmup plan meters. Warmbox publishes a daily warmup volume beside every tier: 50 emails a day on Solo, 250 on Start-up and 500 on Growth. Those are per plan rather than per inbox, so the Growth plan's 500 a day is shared across its six inboxes at roughly 83 each.

Warmbox's published daily warm-up volume per plan. The ceiling belongs to the plan, so Growth's 500 a day is shared across its six inboxes. Lemwarm's pricing page publishes no equivalent figure.

Measure	Value
Solo, 1 inbox	50 emails a day
Start-up, 3 inboxes	250 emails a day
Growth, 6 inboxes	500 emails a day

Lemwarm publishes no equivalent daily figure on its pricing page. It describes the network, the reports and the setup checks, and leaves the ramp to the product. That is not a criticism of either choice, but it does mean the two pages cannot be compared on this axis, and an absence on Lemwarm's page is not evidence of a lower ceiling.

The ramp lemlist's help centre does document, and what the score is made of, are set out in how lemwarm works.

The figure matters because warmup volume has to be sized against sending volume rather than chosen for its own sake. A mailbox sending 30 cold emails a day needs a warmup stream in the same order of magnitude to keep the ratio of real to warmed traffic sensible. On Warmbox's published numbers, six inboxes each sending 30 a day are being warmed at roughly 83 a day each, which is comfortable. Six inboxes each sending 100 a day are not obviously covered, and that is a question to put to the vendor before buying rather than after.

The general habit is worth more than the specific number: read the daily ceiling before the monthly price, because the ceiling is what decides whether the plan does the job at your send volume.

Where the two feature lists actually differ

Every claim below is about what a vendor lists on its own page. Both products warm mailboxes through a network of real accounts, and several entries below describe the same capability in different words.

Lemwarm lists

• Automatic email warm-up
• A warm-up network of 20k+ healthy domains
• Human warm-up emails
• A technical setup check and deliverability reports
• Smart plan Warm-up on your real email templates
• Smart plan A warm-up network tailored to your industry
• lemlist Free with lemlist

Warmbox lists

• Growth, flat or random warm-up
• Fully custom warm-up and a warm-up schedule
• Spam score monitoring
• A live email checker for DNS and blacklists
• A private inboxes network
• 1, 3 or 6 inbox warm-ups, with team members capped to match

Two genuine divergences survive that reading. Warmbox lets you choose the shape of the ramp, offering growth, flat or random curves and a fully custom warm-up, which matters if you are recovering a damaged domain rather than starting a new one. Lemwarm can warm using your real campaign templates on the Smart plan, which is the closer rehearsal for the mail you actually send.

Who should pick which

Switching between them

Neither tool holds data you would need to export, so the migration is a matter of disconnecting mailboxes on one side and connecting them on the other. Both support OAuth for Google and Microsoft and SMTP for everything else, and Warmbox additionally lists Yahoo, iCloud, AOL, Yandex, Zoho, SendGrid, Mailgun and Amazon SES as inbox types.

Run both for a week rather than cutting over in a day. Warmup earns its value through a sustained daily pattern, and a mailbox that stops and restarts reads worse to a provider than one that was never warmed.

Watch the team-member cap when moving to Warmbox. Its plans limit team members to the same number as inboxes, so a three-inbox agency plan seats three people. Lemwarm has no equivalent constraint at the plan level.

Moving the other way, remember to size for growth rather than for today. The Warmbox plan that fits your six inboxes has no room for a seventh, and the next step is a conversation rather than a price.

Where warmup sits in a cold outbound stack

Warmup is infrastructure. It improves the odds a message reaches somewhere a person will look, and it has nothing to say about whether the message deserved to arrive.

That matters more in the way we run campaigns than it does elsewhere. One message per prospect, with no bumps and no thread replies, means a first touch that lands in spam is the whole campaign for that person. There is no follow-up to recover it, so placement carries the full weight and warmup is the cheapest thing that moves placement.

It also explains why mailbox counts in outbound run higher than newcomers expect. Volume comes from many mailboxes each sending modestly, because per-mailbox velocity is the thing providers punish. Both pricing models above are, in effect, charging you for the architecture that keeps you deliverable, and Warmbox's staircase is the one that resists it.

For how a warmup line compares with the rest of the budget, see the cold email pricing guide, and for the field beyond these two, the warmup roundup for cold email teams.

The decision, in one paragraph

Count your mailboxes and check the table. If the number is exactly 1, 3 or 6 and unlikely to move, Warmbox is cheaper, and its plans differ only in capacity and support level. If the number is anything else, or if it grows during the year, Lemwarm's flat $29 a mailbox avoids paying for a bracket you are not filling, and above six inboxes it is the only one of the two still publishing a price. If you pay for lemlist, none of this applies and you should use the warmup you already own.

Related Reading

• Best Lemwarm Alternatives in 2026
• Best Warmbox Alternatives in 2026
• Lemwarm vs Mailreach: Email Warmup Tool Comparison
• Mailreach vs Warmbox: Email Warmup Tool Comparison
• Best Email Warmup Tools for Cold Email Teams

If you would rather not run the infrastructure at all, RevenueFlow books qualified meetings on a pay-per-meeting basis and publishes client results.

Pricing and features are taken from the vendors' own pages. Verify current terms with the vendor before relying on them.