Automated inbox warm-up that builds sender reputation by mailing a private network of real inboxes.
Mailwarm is one of the original inbox warm-up services. The premise is simple: a new mailbox or freshly authenticated domain has no sending history, so Gmail, Outlook and corporate filters treat it with suspicion. Mailwarm sends and receives messages with a private network of real inboxes, marks them as important, replies, removes them from spam, and over four to six weeks builds the reputation a real customer correspondence pattern would create. Done well, this is the difference between a 12 per cent inbox rate and a 75 per cent inbox rate when you start sending real outbound.
Connect a mailbox via Gmail, Microsoft 365 or generic SMTP/IMAP. Authenticate the sending domain with SPF, DKIM and DMARC before warming, otherwise the work is wasted. Set a daily ramp — Mailwarm typically suggests 5–10 emails per day on day one, climbing to 30–50 over four weeks. The platform sends and receives messages with thousands of other warming inboxes; algorithms simulate human reading patterns, replies and spam-folder rescue. A dashboard shows daily volume, reply rate and inbox-placement signals. When you switch to real campaigns, leave warm-up running on a reduced cadence to maintain reputation.
Mailwarm is priced per mailbox per month, with the headline plan around $69/month for 50 daily warm-up emails. There is no free tier — a 7-day trial only. The economics tightened in 2023–2024 as sending platforms (Smartlead, Instantly, SmartReach) bundled free warm-up. If you already pay for Smartlead at $39/month with unlimited warm-up across unlimited mailboxes, Mailwarm's standalone $69/mailbox is hard to justify unless you specifically need its private network reputation or use a sending tool that does not include warm-up.
| Tool | Pricing | Strengths | Weaknesses |
|---|---|---|---|
| Mailwarm | ~$69/mailbox/mo | Original brand, real inboxes | Standalone pricing |
| Warmup Inbox | ~$15/mailbox/mo | Cheap, simple | Smaller network |
| Lemwarm | ~$29/mailbox/mo | Tied to Lemlist | Best inside Lemlist |
| Smartlead/Instantly | Free with sending | Bundled, unlimited mailboxes | Tied to that sender |
Buy if: you send cold email through a platform that does not include warm-up (older Mailshake plans, custom SMTP setups, in-house sending stacks); you run a small number of high-value mailboxes where a strong, established warm-up network materially improves placement; you need a standalone tool because your sending stack changes often and you want warm-up to persist.
Skip if: you already pay for Smartlead, Instantly, SmartReach or another modern sending platform with included warm-up — that is functionally equivalent at no extra cost; you run dozens of mailboxes, where Mailwarm's per-mailbox pricing scales painfully versus bundled alternatives.
7-day trial, $69/month per mailbox after. Best paired with proper SPF, DKIM and DMARC authentication before you start.
Early-stage founders scaling cold email outreach need fast inbox placement. Mailwarm warms new domains before campaigns launch, protecting sender reputation and ensuring leads see the pitch. Founders typically run 1-3 warmup cycles per new domain.
SDRs switching email providers or adding new domains to their stack face deliverability cliffs. Mailwarm keeps accounts warm during transitions, preventing reply rate drops. Teams see consistent performance once the warmup cycle completes.
Agencies managing cold email for 5+ clients need parallel warmup for new sending domains. Mailwarm handles batch account warming, reducing setup time per client. Agencies report faster time-to-first-reply once campaigns go live post-warmup.
Quarterly access to product leadership.
Bonus credits redeemable on partner tooling.
We re-verify the offer every quarter so it never goes stale.
Hit the button on this page — opens the partner site in a new tab.
Check your investor or accelerator benefits portal for the Mailwarm partner code. Y Combinator, Sequoia, and most Tier 1 VCs have codes available.
Renewals stay at the same rate — verified by us, not the vendor.
| Feature | Mailwarm |
|---|---|
| Free trial | 14 days |
| Cheapest paid plan | $0/mo |
| Annual discount | Up to 25% |
| Refund window | 30 days |
| Setup time | < 1 hour |
| Best for | Founders |
“Solid warm-up service but pricier than newer competitors”
“Worth it for high-stakes cold outreach campaigns”
“Inbox placement rate improved from 60% to 89% over 6 weeks”
