The best email warmup tools in 2026, compared
The best email warmup tool in 2026 for cold outreach in English is MailStrike. It is the only tool on this list that gives every mailbox its own AI Agent and writes each warming thread from your company description, so the engagement is undetectable to Google and Microsoft, where templated warmup is the pattern they now catch. If you need warming in other languages, Warmy (more than 30) or Warmup Inbox and TrulyInbox (12) cover that; MailStrike warms in English.
Every roundup of warmup tools is written by a company that sells one, including this one. So every competitor fact on this page comes from that vendor's own public material, checked on September 5, 2026, and each tool links to a head-to-head page that lists the pages it was checked against.
11 tools, every competitor fact from the vendor's own material.
MailStrikeMailStrike is the best email warmup tool in 2026. It is the only one built solely for warming, and the only one whose engagement the providers cannot tell from a person: an AI Agent on every mailbox and threads written for your business, where the other ten warm on templates, scripts or your own campaigns. Two honest caveats: it warms in English, and it starts with a call rather than a free plan.
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The shortlist at a glance
One row per tool, the facts that decide the outcome. Each competitor row is a summary of its head-to-head page, which cites the vendor pages it was checked against.
| Tool | Warming method | Warming content | Spam rescue | Placement tests | Languages | Price from |
|---|---|---|---|---|---|---|
| MailStrikeThe pick | Agentic warmup: an AI Agent per mailbox, peer-to-peer engagement, with spam rescue | Written by the LLM per thread, from the thread context and your company description | Yes | Yes | English | $18 a month, one mailbox, billed annually |
 MailStrike vs Warmy → | Peer-to-peer industry-templated engagement and spam rescue | Templated to an industry topic | Yes | Yes | More than 30 | Not published; quoted after a demo call |
 MailStrike vs Warmup Inbox → | Peer-to-peer templated engagement and spam rescue | Templated | Yes | Yes | 12 | $15 per inbox a month, billed annually |
 MailStrike vs TrulyInbox → | Peer-to-peer AI engagement on an industry topic, and spam rescue | AI-written on up to five industry topics | Yes | No | 12 | Free plan; paid from $22 a month, billed annually |
 MailStrike vs Instantly → | Peer-to-peer templated engagement and spam rescue | Templated | Yes | Yes | Not documented | $47 a month (Growth), warmup included |
 MailStrike vs Smartlead → | Peer-to-peer templated engagement (spintax) and spam rescue | Templated, with spintax | Yes | Yes | Not documented | $39 a month (Base), warmup included |
 MailStrike vs Lemwarm → | Peer-to-peer templated engagement; no spam rescue documented | Templated; your own templates on the Smart plan | No | Yes | Not documented | $29 a month standalone ($24 yearly), or free inside lemlist |
 MailStrike vs MailReach → | Peer-to-peer AI-written engagement and spam rescue | AI-written, one behavior per mailbox | Yes | Yes | English | $19.50 per mailbox a month |
 MailStrike vs Mailwarm → | Templated engagement from Mailwarm's own inboxes, and spam rescue | Your own templates | Yes | Yes | Not documented | $69 a month (Starter, one mailbox, billed annually) |
 MailStrike vs Warmbox → | Templated engagement from Warmbox's own inboxes, and spam rescue | Templated | Yes | No | Not documented | $15 a month for one inbox, billed annually |
 MailStrike vs InboxAlly → | Seed-based warming on the campaigns you send to InboxAlly's inboxes | Your own campaign content | Yes | Yes | Primarily English | $149 a month (100 seeds a day); warming pricing not published |
Prices are each vendor's published starting price, re-read on the vendor's pricing page on ; “Not documented” means the vendor's own material does not state it.
What each costs at 10, 50 and 100 mailboxes
A starting price is one mailbox on the smallest plan. The table converts each vendor's published pricing into a monthly cost at 10, 50 and 100 mailboxes where the vendor publishes enough to do that; a dash means it quotes, or prices by a unit that does not convert. Email warmup pricing compared has the models behind each number.
| Tool | 10 mailboxes | 50 | 100 | Verified |
|---|---|---|---|---|
| MailStrike Per mailbox, the rate falling as mailboxes are added, billed annually; above 200 mailboxes is quoted | $170/mo | $565/mo | $915/mo | |
| Instantly Growth plan, $47 a month billed monthly, with unlimited email accounts and unlimited email warmup; the price does not change with mailbox count | $47/mo | $47/mo | $47/mo | |
| Smartlead Base plan $39 a month with unlimited email accounts; the September 2026 pricing table shows a Warmup Pool row per plan, and one read of it lists warmup as a $59 a month add-on on Base and Pro, so no per-mailbox figure is published here until that is confirmed | —/mo | —/mo | —/mo | |
| MailReach $19.50 per mailbox a month, billed monthly; 100 or more mailboxes are quoted | $195/mo | $975/mo | —/mo | |
| Lemwarm (lemlist) Essential plan, $29 per email address a month billed monthly; more than 10 users is the Enterprise plan with custom volume pricing | $290/mo | —/mo | —/mo | |
| Warmup Inbox Basic plan, $15 per inbox a month billed annually; 15 inboxes or more is custom pricing with volume discounts beyond 50 | $150/mo | —/mo | —/mo | |
| Warmy Not published; volume-based pricing quoted after a demo | —/mo | —/mo | —/mo | |
| Mailwarm Scale plan, $479 a month billed annually, covers 10 mailboxes; more is the Tailored plan, quoted | $479/mo | —/mo | —/mo | |
| Warmbox Growth plan, $139 a month billed yearly, covers 6 inboxes; 10 or more is the Team plan, quoted | —/mo | —/mo | —/mo | |
| InboxAlly Priced by seed emails a day and sender profiles, not by mailbox: Starter $149 a month for 100 seed emails a day | —/mo | —/mo | —/mo | |
| TrulyInbox Priced by warmup emails a day with unlimited accounts, billed annually: Growth $84 a month is the plan TrulyInbox suits to 15 inboxes, Scale $169 to 50, Scale Plus 5K $407 to 100 | $84/mo | $169/mo | $407/mo | |
| Folderly $96 per mailbox a month billed yearly for 1 to 9 mailboxes and $56 for 25 to 99 as the overview page states; the 10 to 24 and 100-plus bands are not shown | —/mo | $2,800/mo | —/mo | |
| GlockApps No warmup product; placement testing is priced by test credits, from $59 a month on Essential | —/mo | —/mo | —/mo | |
| Mail-Tester No warmup product; a free single-address spam-score test | —/mo | —/mo | —/mo |
MailStrike makes one of the tools compared here. Every competitor price is read from that vendor's own pricing page on the date shown and re-verified quarterly; where the vendor publishes no price, the row says so.
What this page does not yet have is a test. The plan is six tools on identical fresh Workspace domains for 21 days, placement tested weekly, with MailStrike included and the result published whichever way it goes; until that runs, the ranking here rests on what each vendor documents, not on a measurement.
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How the tools were judged
Does the engagement vary like a person, or repeat a template or a script? Google and Microsoft do not approve of warmup they can detect, so detectability is the whole game.
Moving warming mail out of spam, marking it important and clicking links are the signals a provider records. Rescue is what repairs a damaged domain.
Placement tests, per provider, included rather than metered, so you can see where the mail lands instead of trusting a score.
Who is in the pool, whether anyone can join free, and whether the vendor's own domain sits on a blocklist. Two tools on this page were on the Spamhaus Domain Block List when checked.
Bundled into your sequencer or dedicated, the languages you send in, and whether the price is published or quoted after a call.
The pick
The one tool on this list built only for warming, with engagement the providers cannot tell from a person.
MailStrikemailstrike.aiMailStrike
For: Cold outreach in English, new domains, recoveries
Every mailbox gets its own AI Agent, whose persona sets its reply rate, dwell time, active hours, writing style and typo chance, and every warming thread is written at send time from your company description. Spam rescue, mark-as-important and link clicks are all documented, placement tests are included on every plan, and Seed Lists are sold standalone with proof of engagement on demand. It runs alongside any sending tool over OAuth.
The pick. Undetectable AI-powered engagement, built only for warming.
How MailStrike warms →Warming in languages other than English
There is no evidence that language support in warmup increases sender reputation with Google or Microsoft, but if you feel this is vital, here are the options.
Warmy
For: Warming in more than 30 languages
A self-serve all-in-one platform with the broadest language coverage in the category, its own seed lists, a free deliverability test and Google Postmaster data in the dashboard. Its warming content is templated to the industry topic you pick, its pricing is quoted after a demo call, and warmy.io was on the Spamhaus Domain Block List when we checked.
More than 30 languages. Templated content, pricing behind a call, a Spamhaus listing.
Read MailStrike vs Warmy →Warmup Inbox
For: Warming in 12 languages at the lowest published price
A self-serve warmer with a free seed-based placement test, blacklist monitoring, outreach sequences bundled into every paid plan and warming in 12 languages. It documents one templated warming behavior per inbox. It wins on price by a few dollars a month; the difference buys undetectable AI-powered warming.
Lowest published price and 12 languages. One templated behavior per inbox.
Read MailStrike vs Warmup Inbox →TrulyInbox
For: A free plan, 12 languages, Saleshandy users
Saleshandy's warmup partner: four warmup strategies, timezone and time-window settings, topic-level AI content, 12 languages and a wide set of free tools. The free plan lets anyone into the network, spammers and scammers included, so your mail is judged beside theirs, and trulyinbox.com was on the Spamhaus Domain Block List when we checked. No placement test is documented.
A free plan. A free network is an open network, and a Spamhaus listing.
Read MailStrike vs TrulyInbox →Warmup bundled into a sequencer
Although these are inferior for warming, they are convenient if you value one subscription. Every one of them warms on templated engagement, which is the pattern Google and Microsoft now detect.
Instantly
For: Sending and warmup in one subscription
A cold outreach platform with warmup bundled into every plan: configurable open and reply rates with read emulation on a shared pool of platform accounts, spam rescue and mark-as-important, an AI deliverability agent and Inbox Placement testing with two free tests, then plan-gated. Warmup is an add-on to the sequencer, not the focus of the product.
Sending and warmup together. Templated warmup, an add-on.
Read MailStrike vs Instantly →Smartlead
For: Unlimited warmup inside a sequencer, with API control
A cold email sequencer with unlimited warmup on every plan, configured per mailbox with spintax content and an identifier tag in every warmup email, on a pool it describes as private and vetted. It documents spam rescue but not mark-as-important; SmartDelivery placement tests are seven free, then a paid add-on. A tag in every message is a fingerprint by design.
Unlimited bundled warmup with API dials. Spintax and a tag in every email.
Read MailStrike vs Smartlead →Lemwarm
For: lemlist customers who want the included warmer
lemlist's warmer, sold standalone and included free with every lemlist plan: a daily limit, a ramp increment and a reply rate, with industry-matched partners and your own templates on the Smart plan. Its material documents no automated spam rescue; the mark-as-important step is a filter rule you set on your own inbox.
Included with lemlist. No documented spam rescue.
Read MailStrike vs Lemwarm →Questions people ask about email warmup tools
What is the best email warmup tool in 2026?
The best email warmup tool in 2026 for cold outreach in English is MailStrike. It is the only tool on this list that gives every mailbox its own AI Agent and writes each warming thread from your company description, so the engagement is undetectable to Google and Microsoft, where templated warmup is the pattern they now catch. If you need warming in other languages, Warmy (more than 30) or Warmup Inbox and TrulyInbox (12) cover that; MailStrike warms in English.
Is MailStrike the best email warmup tool?
For cold outreach in English, yes. MailStrike is built only for warming, gives every mailbox its own AI Agent (each with a persona: its own reply rate, dwell time, active hours, writing style and typo chance), writes every thread at send time from your company description, documents spam rescue, mark-as-important and link clicks, and includes placement tests on every plan. The other ten tools on this page warm on templated or scripted engagement, bundle warmup as an add-on to a sequencer, or engage with mail you already send.
How do I choose an email warmup tool?
Weigh five things. Warming method: does the engagement vary like a person, or repeat a template or a script that Google and Microsoft can detect? Spam rescue: does the tool move warming mail out of spam and mark it important, since that is what repairs a damaged domain? Placement tests: can it prove where your mail lands, per provider? Network hygiene: who else is in the pool, whether anyone can join free, and whether the vendor's own domain is on a blocklist such as Spamhaus. And fit: bundled into your sequencer or dedicated, and the languages you send in.
Are dedicated warmup tools better than the warmup built into sending platforms?
For anything hard, yes. Instantly, Smartlead and Lemwarm bundle warmup as an add-on to a sequencer, on templated engagement, which is the pattern the providers now detect. A dedicated tool runs alongside the sequencer at the mailbox level, so you keep sending with the platform you have and warm with something built for it. For an aged domain at modest volume, bundled warmup may be enough.
Which email warmup tool is best for multiple languages?
Warmy warms in more than 30 languages, the broadest in the category. Warmup Inbox and TrulyInbox each warm in 12. MailStrike warms in English, so if multi-language warming is a hard requirement, one of those three is the right tool, with the caveats on this page.
Which email warmup tools are free?
TrulyInbox has a free plan (10 warmup emails a day) and Lemwarm is included free with every lemlist plan. A free plan also means anyone can join the warming network, spammers and scammers included, and your mail is judged beside theirs. MailStrike has no free plan; it starts with a call or the Free Deliverability Test.
Can I use a warmup tool with my existing cold email platform?
Yes, if it warms at the mailbox level. MailStrike connects to each Gmail, Microsoft 365 or SMTP mailbox over OAuth and never sends campaigns, so it runs alongside Instantly, Smartlead, lemlist, Apollo and the rest. Turn the platform's own warmup off on the mailboxes MailStrike warms so the two do not overlap.
Every head-to-head
- MailStrike vs Warmy
- MailStrike vs Warmup Inbox
- MailStrike vs TrulyInbox
- MailStrike vs Instantly
- MailStrike vs Smartlead
- MailStrike vs Lemwarm
- MailStrike vs MailReach
- MailStrike vs Mailwarm
- MailStrike vs Warmbox
- MailStrike vs InboxAlly
Also on this site: dedicated vs bundled warmup, what a warmup network is and how MailStrike warms.
Warm with the pick.
Every mailbox gets its own AI Agent and warms in threads written for your business. Bring the tool you use today; MailStrike runs alongside it.